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Fuel trim readings got me chasin my tail

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Fuel trim readings got me chasin my tail

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Old 05-31-2018, 12:36 AM
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Default Fuel trim readings got me chasin my tail

Hey everyone,
This is my first time on here so I hope im in the right spot.
Just want to know if anyone out there can help me figure out these fuel trim numbers, cause to me they make no sense at all. Here's what i have;

Bank 1 Bank 2
@ Idle. @ Idle
STFT -- 2.3. STFT --0.8
LTFT --13.3 . LTFT --10.9

@ 2300 RPM . @ 2300 RPM
STFT --2.3 . STFT --17.2
LTFT 21.1. LTFT 21.9

UNDER LOAD . UNDER LOAD
@ 2000 RPM . @ 2000 RPM
STFT 22.7. STFT 18.8
LTFT 32.O. LTFT 32.8

To me these numbers dont make any sense cause the way I read this at idle the pcm is taking away fuel when it should be adding to compensate for LTFT numbers. At 2300 rpm it makes more sense but not good numbers. Then again under load the same thing is happening but the pcm is adding fuel with already high LTFT numbers.
Please correct me if i'm wrong and set me straight cause i'm running out of hair to pull out.

Thanks everyone for your input and helping me figure this out.

Goinwheelin


Oh Btw its a 98 f 150 4.6 4x4 with 242000 km and I have changed a lot of parts. Heres a list of what ive done;

Plugs
Plug wires
Both coil packs
Fuel filter
Fuel pressure regulator
Tps
Egr tube
Evap hose
Exhaust manifolds
Cleaned the maf
Cleaned all 8 injectors
Also ive had this truck from new and its never given me any problem at all so its kinda like my child so putting new parts in it doesnt hurt considering i have less than 1000 bucks into it in repairs prior to this.

Last edited by goinwheelin; 05-31-2018 at 12:21 PM. Reason: Add more info
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Old 06-02-2018, 07:05 PM
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Why are you worrying about the intricacies of the EEC's adaptions? Is there some symptom you noticed while driving? Is there a fault code (number AND complete definition)? Why are you changing non-maintenance-schedule parts? For EACH ONE, you need to explain when (time/miles), why (symptom/diagnostic steps), what (brand, PN, source), and whether the replacement passed the same test the original failed. You should NOT have cleaned the MAF - that alone could cause many driveability & adaption problems. My truck's engine has ~860Kmi without a rebuild, and I've never cleaned the injectors (other than pour-in) even though they were stuck closed when I pulled the engine out of a junkyard 20 years ago.
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Old 06-02-2018, 10:44 PM
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Default Fuel trim numbers

Sorry Steve , I forgot to mention that I have the P0171 and P0174 lean codes bank 1 and 2.
When I originally got these codes my truck almost never made it home, it would idle fine but as soon as i put it in gear and stepped on the gas it would almost die immediately. It sounded to me like it was flooding. Thats when I changed the fuel pressure regulator and TPS but nothing changed.So then i got the codes pulled for me and saw it was the P0171 and P0174 lean codes. Most of the other parts I replaced was because they needed to be with the exception of the coil packs.
As for mileage the truck hasn't been driven very much at all, less than 100 kms cause it wasnt insured. This has been done over quite some time.
As for the MAF sensor and injector cleaning, I just used MAF sensor spray cleaner, and I didnt think pulling the injectors and cleaning them was a big deal considering the mileage and as well I could bench test them while they were out.
I really do appreciate your advice and apologize if I have sent you any misconseptions with my explanations.

Thanks
Goinwheelin
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Old 06-03-2018, 01:34 AM
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Not to jump in on too far on Steve83's advice, but the "trim": numbers are really just directly related to how long the injectors are staying open in order to make the O2 senor readings correct. The PCM or ECM or EEC, the computer, just adds more injector open time until the O2 sensor says it's close to stoichiometric. The + or - is based on what "should" happen, more injector open time or less time, based on the engineer's original map for a perfect engine. So, high trim numbers mean either that there's an air leak after the MAF sensor, or that not as much fuel is squirting as should be when the injectors are open.

Your post is confusing because you have the -- in front of some numbers. Is that supposed to be a negative sign? Why are there two negative signs? You said that you're getting lean codes, which fits the high "under load" numbers. Do you have Freeze Frame data? You have to pull it from the PCM using your OBD scanner.

It is possible to get negative trims. Oil burning would look like fuel to the O2 sensors.
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Old 06-03-2018, 08:04 AM
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May seem like I'm being captain obvious but what are the fuel pressure readings eg: Idle - 2000rpms? Also what condition is the air filter in, has it been changed? Was it installed backwards? <------ I've seen it happen the plastic bullet nose should be installed pointing away from the engine.
.

Last edited by Rnlcomp; 06-03-2018 at 08:10 AM.
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Old 06-03-2018, 12:56 PM
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Originally Posted by goinwheelin View Post
...I forgot to mention that I have the P0171 and P0174 lean codes bank 1 and 2.
Fuel trims are not part of the diagnostic process for those faults.
Originally Posted by goinwheelin View Post
Thats when I changed the fuel pressure regulator and TPS...
Why? What diagnosis led you to those parts? Did the new parts pass the same tests the originals failed?
Originally Posted by goinwheelin View Post
Most of the other parts I replaced was because they needed to be...
Based on WHAT, for EACH part?
Originally Posted by goinwheelin View Post
...with the exception of the coil packs.
Then why was each one changed?
Originally Posted by goinwheelin View Post
This has been done over quite some time.
Vagueness... Be specific. Some people consider a week of working on a vehicle to be "quite some time". Other people take years.
Originally Posted by goinwheelin View Post
...I just used MAF sensor spray cleaner...
Yeah, that's what I thought. But since you didn't say what brand, or if you read the instructions on the can, or what came out of the MAF, or if cleaning had any effect, I'm saying it was a risky move.
Originally Posted by goinwheelin View Post
... I didnt think pulling the injectors and cleaning them was a big deal ...
It's not - it's just not necessary, either. And messing around with things that don't need messed can mess other things up.

This formatting may not translate to the forum, but with some effort, you should be able to follow it:
Originally Posted by 1997 PCED On Board Diagnostics II A, SECTION 5A: Pinpoint Tests
H41 DTCs P0172, P0174, P0171 AND P0175: FUEL SYSTEM AT THE CORRECTED FUEL TRIM
Diagnostic Trouble Codes (DTCs) P0171 bank 1 (Cylinder 1) and DTC P0174 bank 2 indicate the fuel/air ratio is too lean. The fuel trim system is at the rich correction limit.

DTC P0172 bank 1 and DTC P0175 bank 2 indicate the fuel/air ratio is too rich. The fuel trim system is at the lean correction limit.

DTCs HO2S Reference list:
  • HO2S-11 = DTCs P0171 and P0172
  • HO2S-21 = DTCs P0174 and P0175
Possible causes:

Fuel system
    • Excessive fuel pressure.
    • Leaking fuel injector(s).
    • Leaking fuel pressure regulator.
    • Low fuel pressure or running out of fuel.
    • Contaminated fuel injector(s).
    • Vapor management valve (VMV) leaking.
Induction system
    • Air leaks after the MAF.
    • Vacuum leaks (vacuum lines and gaskets).
    • Restricted air inlet.
    • PCV system.
    • Fuel purge system.
    • Improperly seated engine oil dipstick.
EGR System
    • leaking gasket.
    • Stuck open EGR valve.
    • Leaking diaphragm.
Base engine
    • Oil overfill.
    • Cam timing.
    • Cylinder compression.
    • Exhaust leaks before or near the HO2S(s).
  • Check intake air system for leaks, obstructions and damage.
  • Check air cleaner element, air cleaner housing for blockage.
  • Verify integrity of the PCV system.
  • Check for vacuum leaks.
Are any of the above concerns present?
Yes SERVICE as necessary. RERUN Quick Test .
No COMPLETE PCM Reset to clear DTCs. GO to H42 .

H42 PERFORM KOER SELF-TEST
  • Key off.
  • Scan Tool connected.
  • Disconnect fuel vapor hose from intake manifold and plug fitting at intake manifold.
  • Start engine and run at 2000 rpm for 5 minutes and return to idle.
  • Perform Key On Engine Running (KOER) Self-Test.
For Continuous DTCs Only P1130, P1150, P0171, P0174, P0172 and P0175:

GO to H52 .

H52 CHECK FUEL PRESSURE

WARNING: THE FUEL SYSTEM IS PRESSURIZED WHEN THE ENGINE IS NOT RUNNING. TO PREVENT INJURY OR FIRE, USE CAUTION WHEN WORKING ON THE FUEL SYSTEM. BECOME FAMILIAR WITH THE WARNING CAUTION AND NOTE IN PINPOINT TEST HC BEFORE SERVICING.
  • Key off.
  • Install fuel pressure gauge.
  • Verify vacuum source to fuel pressure regulator.
  • If engine will start:
  • Start engine and idle. Record fuel pressure.
  • Increase engine speed to 2500 rpm and maintain for one minute. Record fuel pressure.
  • No Start:
  • Cycle key on and off several times. Record fuel pressure.
Is the fuel pressure between 310-415 kPa (45-60 psi) for (2.5L) Contour/Mystique or 207-310 kPa (30-45 psi) for all others?YesNoFuel system is capable of required fuel pressure. GO to H53 .Probe:

Fuel pressure out of specification.

GO to Pinpoint Test KN1 .

All others:

GO to Pinpoint Test HC1 .H53 CHECK SYSTEM ABILITY TO HOLD FUEL PRESSURE
  • Fuel pressure gauge installed.
  • Cycle key on and off several times.
  • Verify there are no external leaks (service as necessary).
Does the fuel pressure remain within 34 kPa (5 psi) of the highest reading after one minute?YesNoFor Continuous DTCs P1130, P1150, P0171, P0172, P0174 and P0175:

GO to H54 .

For No Starts:

GO to H55 .

For HO2S DTCs displayed with misfire DTCs: GO to H56 .

Flexible Fuel Taurus:

GO to H56 .

All other DTCs:

GO to H60 .Excessive pressure loss. GO to Pinpoint Test Step HC4 .H54 CHECK SYSTEM ABILITY TO HOLD FUEL PRESSURE WITH KEY ON
  • Fuel pressure gauge installed.
  • Cycle key on then off several times.
  • Turn key on and engine off, monitor fuel pressure gauge.
Does the fuel pressure remain within 34 kPa (5 psi) of the highest reading after 10 seconds?YesNoFor Continuous DTCs P1130, P1150, P0171 and P0174:

GO to H56 .For DTCs P0172 and P0175:

GO to H58 .H55 CHECK ABILITY OF FUEL INJECTOR(S) TO DELIVER FUEL
  • Pressure gauge installed.
  • Cycle key several times.
  • Locate and disconnect the Inertia Fuel Shutoff (IFS) Switch.
  • Monitor pressure gauge while cranking the engine for at least five seconds.
Was there a pressure drop greater than 34 kPa (5 psi) while cranking the engine?YesNoThe Electronic Engine Control System is not the cause of the no start. REMOVE the fuel pressure gauge. RECONNECT the IFS switch. REFER to Section 3A , Symptom Charts, for further diagnosis.REMOVE fuel pressure gauge. RECONNECT IFS switch. GO to H56 .H56 CHECK RESISTANCE OF FUEL INJECTOR(S) AND HARNESS
  • Key off.Note: This erases Continuous Memory DTCs.
  • Disconnect PCM. Inspect for damaged or pushed out pins, corrosion and loose wires. Service as necessary.
  • Install breakout box, leave PCM disconnected.Note: If misfire DTCs are displayed with the Fuel Control DTCs, use the misfire DTCs to determine the fuel injector circuits requiring testing.
  • Measure resistance between suspect fuel injector Test Pin(s) and Test Pin 71/97 (VPWR) at the breakout box using the chart below.FUEL INJECTOR TEST PINSCylinder NumberTest PinCylinder NumberTest Pin175699210177237489841009685731042
Is the resistance between 11.0-18.0 ohms?YesNoFuel injector and harness resistance is OK. GO to H59 .GO to H57 .H57 CHECK RESISTANCE OF FUEL INJECTOR HARNESS
  • Key off.
  • Breakout box installed, PCM disconnected.
  • Disconnect fuel injector harness connector at the suspect fuel injector.
  • Measure the resistance between Test Pin 71/97 (VPWR) at the breakout box and the VPWR pin at the fuel injector harness connector.
  • Measure resistance between the Fuel Injector Test Pin(s) at the breakout box and the Fuel Injector Signal Pin at the fuel injector connector. (Refer to chart in H56 for Fuel Injector Pin location.)
Is each resistance less than 5.0 ohms?YesNoGO to H58 .SERVICE open harness circuit. REMOVE breakout box. RECONNECT PCM and fuel injectors. RERUN Quick Test .

Last edited by Steve83; 06-13-2018 at 12:04 PM.
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Old 06-03-2018, 01:00 PM
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Continued...
Originally Posted by 1997 PCED On Board Diagnostics II A, SECTION 5A: Pinpoint Tests
H58 CHECK FUEL INJECTOR HARNESS CIRCUIT FOR SHORT TO POWER OR GROUND
  • Key off.
  • Breakout box installed, PCM disconnected.
  • Suspect fuel injector harness disconnected.
  • Measure resistance between the fuel injector Test Pin(s) and Test Pin 71 or 97 (VPWR), 24 and 103 (PWR GND) at the breakout box (refer to chart in H56 ).
  • Measure the resistance between the Fuel Injector Test Pin(s) at the breakout box and chassis ground.
Is each resistance greater than 10,000 ohms?YesNoGO to H59 .SERVICE short circuit. REMOVE breakout box. RECONNECT PCM and all fuel injector(s). RERUN Quick Test .

H59 CHECK INJECTOR DRIVER SIGNAL

This test requires a standard 12 volt test lamp.
  • Key off.
  • Breakout box installed.
  • Connect PCM to breakout box.
  • Connect test lamp between Test Pin 71/97 (VPWR) and suspect fuel injector Test Pin(s) (refer to chart in H56 ).Note: Properly operating system will show a dim glow at idle on the test lamp.
  • Crank or start engine.
Does test lamp have a dim glow while cranking or running engine?YesNoREMOVE breakout box. RECONNECT PCM. GO to H60 .No light/Continuous bright light. REPLACE PCM. REMOVE breakout box. RERUN Quick Test .

H60 FLOW TEST FUEL INJECTOR(S)

  • Use the Rotunda Injector Tester, SBDS® Injector Tester or equivalent to flow test the fuel injectors according to the instructions for the fuel injector tester.
Is the leakage and flow within specification?YesNoDTCs P0171, P0174:

GO to H62 .

DTCs P0172 and P0175:

The fault that produced the DTC is an intermittent. GO to Pinpoint Test Step Z1 with the following data: SF1, SF2, LFT1, LFT2 PIDs and list of Possible causes.

For DTCs P1130 and P1150:

GO to H62 .

For DTCs P1131 and P1151:

GO to H61 .

For DTCs P1132 and P1152:

GO to H65 .REPLACE fuel injector. COMPLETE PCM Reset to clear DTCs. RERUN Quick Test.

H61 CHECK FOR SECONDARY AIR INTRUSION

Note: If the vehicle is not equipped with Secondary Air Injection System, GO to H62 .

An HO2S always lean condition can be caused by:
    • Leak in hoses from Secondary Air Injection pump to engine.
    • Secondary Air diverted upstream of HO2S.
  • Key off.
  • Disconnect Secondary Air Injection hose(s) from engine and plug engine side of secondary air injection system.
  • Key on, engine running and at operating temperature.
  • Activate Key On, Engine Running (KOER) Self-Test.
Are DTC(s) P1131 or P1151 present?YesNoRECONNECT secondary air injection hose and GO to H62 .Cause of DTC(s) is in the Secondary Air Injection System. GO to HM7 for Secondary Air Injection System diagnostics.

H62 INSPECT INDUCTION SYSTEM FOR AIR LEAKS

  • Inspect the following areas for signs of air leaks:
    • Inlet tube(s) from air cleaner to the throttle body.
    • Gaskets which seal the upper and lower intake manifold.
    • Vacuum hoses and lines for cracks and proper connections.
    • PCV system.
Are there any signs of leaks or damage?YesNoSERVICE as necessary. COMPLETE PCM Reset to clear DTCs. RERUN Quick Test .CONTINUOUS DTCs P0171, P0174, P1130 or P1150:

The fault that produced the DTC is an intermittent. GO to Pinpoint Test Step Z1 with the following data: SF1, SF2, LFT1, LFT2, HO2S-11 and HO2S-21 PIDs and a list of Possible causes.

DTCs P1131 and P1130 or P1151 and P1150:

GO to H63 .

H63 CHECK CYLINDER COMPRESSION

Note: Use the Misfire DTC(s) displayed on prior DTC retrieval to determine which cylinder's compression to check.
  • Check cylinder compression. Refer to Powertrain/Engine Group, Base Engine/Engine—Service Section in the Service Manual.
Are cylinder compression readings within specification?YesNoFor DTCs P1131, P1130, P1151 and P1150:

GO to H64 .

For DTCs P1132 and P1152:

GO to H65 .

Misfire DTCs displayed with fuel control DTCs:

GO to HD20 .SERVICE as necessary. COMPLETE PCM Reset to clear DTCs. RERUN Quick Test .

H64 CHECK HO2S ABILITY TO GENERATE A VOLTAGE GREATER THAN 0.5 VOLT

Any vacuum or air leaks can cause DTCs P1131, P1151, P1130 and P1150.

Possible causes:
    • Leaking vacuum actuators.
    • Engine sealing (Intake and IAC).
    • EGR system (valve).
    • PCV system (hose and valve).
    • Unmetered air leaks between throttle body and Mass Air Flow (MAF) sensor assembly.
    • Silicone contaminated HO2S.
  • Key off.
  • Inspect HO2S harness for chafing, burned out wires or other damage and service as necessary.
  • Disconnect the suspect HO2S from vehicle harness.
  • Connect digital multimeter to the HO2S Signal and HO2S SIG RTN or HO2S GND at the HO2S sensor connector.
  • Run engine at 2000 rpm for three minutes.
  • Rerun KOER Self-Test and monitor HO2S voltage.
Is the voltage greater than 0.5 volt during or at the end of Self-Test?YesNoGO to H70 .REPLACE HO2S. RERUN Quick Test .

H65 ATTEMPT TO GENERATE DTCS P1131 AND P1151

  • Key off.
  • HO2S disconnected.
  • Jumper HO2S Signal at the HO2S harness vehicle connector to the battery negative post.
  • Activate Key On Engine Running (KOER) Self-Test.
Are DTCs P1131 or P1151 present?YesNoREMOVE jumper. GO to H66 .REMOVE jumper. RECONNECT HO2S. DISCONNECT PCM. INSPECT both ends of connector for damaged or pushed out pins, moisture, corrosion, loose pins and SERVICE as necessary. If OK, REPLACE PCM. RERUN KOER Self-Test.

H66 HO2S CHECK

  • Key off.
  • Suspect HO2S disconnected.
  • Connect digital multimeter to HO2S SIG circuit and HO2S SIG RTN at the HO2S sensor connector.
  • Disconnect vacuum hose from vacuum tree.
  • Start engine and run at 2000 rpm.
Does the voltage reading indicate less than 0.4 volt within 30 seconds?YesNoRECONNECT vacuum hose and HO2S. GO to H70 .REPLACE HO2S. RECONNECT vacuum hose. RERUN Quick Test .

H70 MONITOR HO2S (PID) FOR PROPER SWITCHING

  • Key on, engine running.
  • Engine at operating temperature.Note: HO2S displayed as O2S on Scan Tool.
  • Monitor suspect HO2S PID using Scan Tool.
  • Access HO2S PID while wiggling, bending, and shaking small sections of the Electronic Engine Control harness from the PCM to the HO2S.
Did the HO2S voltage stay high (greater than 0.45 volt) or low (less than 0.45 volt)?YesNoISOLATE cause of lack of HO2S switches and service. COMPLETE PCM Reset to clear DTCs. RERUN Quick Test .GO to H71 .
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Continued...
Originally Posted by 1997 PCED On Board Diagnostics II A, SECTION 5A: Pinpoint Tests
H71 TEST DRIVE WHILE MONITORING HO2S PID FOR PROPER SWITCHING
Note: This test step requires an observer to monitor PID for proper operation.
  • Scan Tool still attached.
  • Access HO2S PID.
  • While observer views PID, test drive vehicle under different road conditions in an attempt to simulate the original fault.
Does HO2S appear to switch properly?YesNoUNABLE to duplicate fault. COMPLETE PCM Reset to clear DTCs. Testing complete at this time.REPLACE HO2S. COMPLETE PCM Reset to clear DTCs. RERUN Quick Test .

H80 DTCS P0136 AND P0156 MONITOR DOWNSTREAM HO2S OUTPUT VOLTAGE FOR ACTIVITY. DTCS P1137, P1138, P1157 AND/OR P1158 INDICATE LACK OF HO2S SWITCHING

DTC P0136 and P0156 indicate the output voltage of the downstream HO2S is less than some calibratable functional window. KOER DTCs P1137, P1138, P1157 and P1158 can only be retrieved during KOER Self-Test when the fuel control is ramped rich and lean and monitored for a voltage change on the downstream HO2S.

Possible causes:
    • DTC P0136, P1137 and P1138=HO2S-12
    • DTC P0156, P1157 and P1158=HO2S-22
  • Wiring Concerns:
    • Pinched, shorted, and corroded wiring and pins
    • Crossed sensor wires
  • Other Concerns:
    • Exhaust leaks
    • Contaminated or damaged sensor
Are any of the above concerns present?YesNoSERVICE as necessary. COMPLETE PCM Reset to clear DTCs. RERUN Quick Test .Continuous Memory DTCs P0136 and P0156:

GO to H81 .

All others:

GO to H82 .

H81 CHECK FOR KOER DTCS P1137, P1138, P1157 AND P1158

  • Key off.
  • Scan Tool connected.
  • Key on.
  • Engine at 2000 rpm for 3 minutes.
  • Activate KOER Self-Test.
  • Check for DTCs.
Are DTCs P1137, P1138, P1157 or P1158 present?YesNoGO to H82 .For DTCs P0136 and P0156:

The fault that produced the DTC is intermittent. GO to Pinpoint Test Step Z1 with the following data: HO2S-12,22 PIDs and list of Possible causes.

H82 CHECK EXHAUST SYSTEM FOR LEAKS

Note: Any exhaust leaks between the engine and the end of the catalyst can cause DTCs P0136 and P0156.
  • Key off.
  • Place vehicle on a hoist, transmission in PARK, emergency brake applied, raise vehicle.
  • Inspect the following:
    • Exhaust flanges for leaks.
    • HO2S torque.
    • Check for punctures and cracks in catalyst and pipes leading to them.
Are there any exhaust leaks?YesNoREPLACE or SERVICE as required. COMPLETE PCM Reset to clear DTCs. RERUN Quick Test .GO to H83 .

H83 CHECK HO2S HARNESS CIRCUIT FOR SHORT TO VPWR AND GROUND

  • Key off.
  • Disconnect Scan Tool from DLC.
  • Disconnect PCM. Inspect both ends of connector for damaged or pushed out pins, moisture, corrosion and loose pins. Service as necessary.
  • Install breakout box. Leave PCM disconnected.
  • Suspect HO2S disconnected.
  • Measure the resistance between HO2S Signal Test Pin and SIG RTN Test Pin at the breakout box.
  • Measure the resistance between HO2S Signal Test Pin and VPWR and VREF Test Pin at the breakout box.
  • Measure the resistance between HO2S Signal Test Pin and PWR GND Test Pin at the breakout box.
    • HO2S-12 SIG = Test Pin 35
    • HO2S-22 SIG = Test Pin 61
    • HO2S SIG RTN = Test Pin 91
    • PWR GND = Test Pins 24 and 103
    • VPWR = Test Pins 71 and 97
    • VREF = Test Pin 90
Is resistance greater than 10,000 ohms?YesNoGO to H84 .SERVICE short in harness. REMOVE breakout box. RECONNECT PCM. RERUN Quick Test .

H84 CHECK RESISTANCE OF HO2S AND HO2S GROUND CIRCUITS

  • Key off.
  • Breakout box installed, PCM disconnected.
  • Suspect HO2S disconnect from harness.
  • Measure the resistance between HO2S Signal Test Pin at the breakout box and the HO2S vehicle harness connector. Record readings.
  • Measure resistance between SIG RTN Test Pin at the breakout box and HO2S SIG RTN vehicle harness connector. Record readings.
    • HO2S-12 SIG = Test Pin 35
    • HO2S-22 SIG = Test Pin 61
    • HO2S SIG RTN = Test Pin 91
Is the resistance reading less than 5.0 ohms?YesNoGO to H85 .SERVICE open circuit in harness. REMOVE breakout box. RECONNECT all components. RERUN Quick Test .

H85 CHECK HO2S CIRCUIT RESISTANCE

  • Key off.
  • PCM connected to vehicle harness.
  • Suspect HO2S connected to vehicle harness.
  • Scan Tool connected.
  • Key on, engine off.Note: HO2S displayed as O2S on Scan Tool.
  • Access the correct HO2S PID.DTCHO2SPINSP0136, P1137 and P1138HO2S-1235 and 91
Is the voltage greater than 1.5 volts?YesNoGO to H88 .GO to H86 .

H86 CHECK RESISTANCE OF HO2S GROUND CIRCUIT IN THE PCM

  • Key off.
  • PCM connected to breakout box. Vehicle harness disconnected from breakout box.
  • Measure the resistance between SIG RTN Test Pin and PWR GND Test Pin at the breakout box.
Is the resistance reading less than 5.0 ohms?YesNoREMOVE breakout box. RECONNECT PCM. GO to H87 .REPLACE PCM. REMOVE breakout box. RECONNECT all components.

H87 APPLY 12 VOLTS TO SUSPECT HO2S CIRCUIT

  • Key off.
  • Suspect HO2S disconnected.
  • Jumper VPWR to HO2S signal circuit at the vehicle harness connector.
  • Key on.
  • Access HO2S PID and monitor.
Is the PID value greater than 1.5 volts?YesNoREPLACE HO2S. RECONNECT all components. COMPLETE an HO2S Monitor Repair Verification Drive Cycle (REFER to Section 2A, Drive Cycles ). RERUN Quick Test .REPLACE PCM. RECONNECT all components. COMPLETE an HO2S Monitor Repair Verification Drive Cycle (REFER to Section 2A, Drive Cycles ). RERUN Quick Test .

H88 CHECK FOR OVER VOLTAGE ON THE HO2S CIRCUIT IN THE PCM

  • Key on.
  • PCM connected to vehicle harness.
  • HO2S disconnected.
  • Inspect both ends of connector for damaged or pushed out pins, moisture, corrosion and loose pins. Service as necessary.
  • Measure the voltage between SIG RTN Test Pin at the HO2S vehicle harness connector and battery negative post.
  • Measure the voltage between HO2S SIG Test Pin at the HO2S vehicle harness connector and battery negative post.
Are the voltage readings greater than 1.5 volts?YesNoREPLACE PCM. RECONNECT all components. RERUN Quick Test .REPLACE HO2S. RECONNECT all components. RERUN Quick Test .
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Old 06-03-2018, 07:55 PM
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Default More test results

Thanks everyone for you help on this. I did a couple more tests today, vacuum and fuel pressure so heres the results;

Vacuum
@ idle 21 in-Hg steady
Snap throttle. Vacuum peaked or zeroed, then went to 26 in-Hg for a couple seconds and then went back to 21 in-Hg steady.

Fuel pressure
Key on engine off. 36 psi
@ idle. 30 psi
Vacuum disconected @ fuel pressure reg. 40 psi
@2000 rpm. 30 psi
Pressure after 5 min. shutdown 36 psi.

I did these tests 3 times each but on the 2nd fuel test the pressure after shutdown bled of to10 psi in about 1 or 2 min. That doesn't sound right.
What could cause that?
Is this something that would cause lean codes?

Thanks again everyone.
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Old 06-03-2018, 08:06 PM
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Originally Posted by Steve83 View Post
Fuel trims are not part of the diagnostic process for those faults.
They might not be called out specifically in the written Ford documents but they sure do tell a story hat will help you solve the problem.

The logic can be extracted from the documented procedure, and understanding trims. High trims are typically a sign of air leaks. The book is nice but you can go beyond the book too.

H62 INSPECT INDUCTION SYSTEM FOR AIR LEAKS

  • Inspect the following areas for signs of air leaks:
    • Inlet tube(s) from air cleaner to the throttle body.
    • Gaskets which seal the upper and lower intake manifold.
    • Vacuum hoses and lines for cracks and proper connections.
    • PCV system.
Are there any signs of leaks or damage?YesNoSERVICE as necessary. COMPLETE PCM Reset to clear DTCs. RERUN Quick Test .CONTINUOUS DTCs P0171, P0174, P1130 or P1150:
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