dewman

The check engine light came on today. I stopped by the local AutoZone because they will put their reader on the truck and give you the code and the reason for free.

P0136: O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)
The guy at the store said that would be the O2 sensor
that comes after the cat.

My question for you is this: Is this a problem with the sensor, or the circuit the sensor is on? And what can I do to fix it?

Thanks again!

svt tech

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:
• 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?
Yes No SERVICE as necessary. COMPLETE PCM reset to clear DTCs (REFER to Section 2A, Powertrain Control Module (PCM) Reset ). 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 5 minutes.
• Activate KOER Self-Test.
• Check for DTCs.

Are DTCs P1137, P1138, P1157 and P1158 present?
Yes No GO to H82 . For DTCs P0136 and P0156:

The fault that produced the DTC is an 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 may 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?
Yes No REPLACE or REPAIR as required. COMPLETE PCM reset to clear DTCs (REFER to Section 2A, Powertrain Control Module (PCM) Reset ). RERUN Quick Test. GO to H83 .
H83 CHECK HO2S HARNESS CIRCUIT FOR SHORT TO VPWR AND GROUND

• Key off.
• Disconnect Scan Tool from DLC.
• Breakout box installed, PCM disconnected. Inspect both ends of connector for damaged or pushed out pins, moisture, corrosion, loose pins, etc. and service as necessary.
• 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?
Yes No GO to H84 . SERVICE short in harness. COMPLETE PCM reset to clear DTCs (REFER to Section 2A, Powertrain Control Module (PCM) Reset ). RERUN Quick Test.
H84 CHECK CONTINUITY OF HO2S AND HO2S GROUND CIRCUITS

• Key off.
• Breakout box installed, PCM disconnected.
• Disconnect suspect HO2S 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?
Yes No GO to H85 . REPAIR open circuit in harness. REMOVE breakout box. RECONNECT all components. RERUN Quick Test.
H85 CHECK HO2S CIRCUIT CONTINUITY

• Key off.
• PCM connected to vehicle harness.
• Suspect HO2S connected to vehicle harness.
• Scan Tool connected.
• Key on, engine off.
• Access the correct HO2S PID. Note: HO2S displayed as O2S on Scan Tool.
  
  
  DTCHO2SPINSP0136HO2S-1235 and 91P0156HO2S-2261 and 91

Is the voltage greater than 1.5 volts?
Yes No GO to H88 . GO to H86 .
H86 CHECK CONTINUITY 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?
Yes No REMOVE 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.
• Accesss HO2S PID and monitor.

Is the PID value greater than 1.5 volts?
Yes No REPLACE HO2S. RECONNECT all components. COMPLETE an HO2S Monitor Drive Cycle (REFER to Section 2A, Drive Cycles ). RERUN Quick Test. REPLACE PCM. RECONNECT all components. COMPLETE an HO2S Monitor Drive Cycle (REFER to Section 2A, Drive Cycles ). RERUN Quick Test.

svt tech

H90 DTCS P0136 AND P0156: MONITOR DOWNSTREAM HO2S OUTPUT VOLTAGE FOR ACTIVITY

• [*]
• [*]

Are any of the concerns present?
Yes No SERVICE as necessary. COMPLETE PCM reset to clear DTCs (REFER to Section 2A, Powertrain Control Module (PCM) Reset ). COMPLETE a HO2S monitor drive cycle (REFER to Section 2A, Drive Cycle ) RERUN Continuous Memory Self-Test. GO to H91 .
H91 CHECK FOR CROSSED HO2S HARNESS CONNECTOR

• Key off.
• Disconnect the HO2S that corresponds to the DTCs.
  
  HO2SOriginal DTCHeater DTCHO2S-12P0136P0141HO2S-22P0156P0161
• Activate KOEO Self-Test.

Is a corresponding HO2S HTR DTC generated?
Note: Disregard any DTCs other than HO2S HTR codes.
Yes No DTCs correspond to correct HO2S location indicating HO2S are not crossed. GO to H92 . CHECK for crossed HO2S and wiring. REFER to schematic for correct HO2S pin location. COMPLETE an HO2S Monitor Drive Cycle (REFER to Section 2A, Drive Cycles ). RERUN Continuous Memory Self-Test.
H92 CHECK EXHAUST SYSTEM FOR LEAKS

• [*]
• [*]
• [*]

Are there any exhaust leaks?
Yes No REPLACE or REPAIR as required. COMPLETE PCM reset to clear DTCs (REFER to Section 2A, Powertrain Control Module (PCM) Reset ). COMPLETE a HO2S Monitor Drive Cycle (REFER to Section 2A, Drive Cycles ). RERUN Continuous Memory Self-Test. GO to H93 .
H93 CHECK HO2S HARNESS CIRCUIT FOR SHORT TO VPWR AND GROUND

• Key off.
• Disconnect Scan Tool from DLC.
• Breakout box installed, PCM disconnected. Inspect both ends of connector for damaged or pushed out pins, moisture, corrosion, loose pins, etc. and service as necessary.
• 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?
Yes No GO to H94 . SERVICE short in harness. COMPLETE PCM reset to clear DTCs (REFER to Section 2A, Powertrain Control Module (PCM) Reset ). COMPLETE a HO2S Monitor Drive Cycle (REFER to Section 2A, Drive Cycles ). RERUN Continuous Memory Self-Test.
H94 CHECK CONTINUITY OF HO2S AND HO2S GROUND CIRCUITS

• Key off.
• Breakout box installed, PCM disconnected.
• Disconnect suspect HO2S 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?
Yes No GO to H95 . REPAIR open circuit in harness. REMOVE breakout box. RECONNECT all components. RERUN Quick Test. COMPLETE a HO2S Monitor Drive Cycle (REFER to Section 2A, Drive Cycles ). RERUN Continuous Memory Self-Test.
H95 CHECK HO2S CIRCUIT CONTINUITY

• Key off.
• PCM connected to vehicle harness.
• Suspect HO2S connected to vehicle harness.
• Scan Tool connected.
• Key on, engine off.
• Access the correct HO2S PID. Note: HO2S displayed as O2S on Scan Tool.
  
  
  DTCHO2SPINSP0136HO2S-1235 and 91P0156HO2S-2261 and 91

Is the voltage greater than 1.5 volts?
Yes No GO to H97 . GO to H96 .
H96 CHECK CONTINUITY 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?
Yes No REPLACE HO2S. REMOVE breakout box. RECONNECT all components. COMPLETE a HO2S Monitor Drive Cycle (REFER to Section 2A, Drive Cycles ). RERUN Continuous Memory Self-Test. REPLACE PCM. REMOVE breakout box. RECONNECT all components. COMPLETE a HO2S Monitor Drive Cycle (REFER to Section 2A, Drive Cycles ). RERUN Continuous Memory Self-Test.
H97 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, loose pins, etc. and 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 Signal Test Pin at the HO2S vehicle harness connector and battery negative post.

Are the voltage readings greater than 1.5 volts?
Yes No REPLACE PCM. RECONNECT all components. RERUN Quick Test. COMPLETE a HO2S Monitor Drive Cycle (REFER to Section 2A, Drive Cycles ). RERUN Continuous Memory Self-Test. REPLACE HO2S. RECONNECT all components. RERUN Quick Test. COMPLETE a HO2S Monitor Drive Cycle (REFER to Section 2A, Drive Cycles ). RERUN Continuous Memory Self-Test.

wde3477

now if this isn't an example of 'be careful what you ask for' :-)

dewman

LOL!!

dewman

Thank you svt tech!

That is/was a whole lot more than I will be capable of doing myself.
I do not have any testers or other equipment to check voltage, etc.
Nor would I really know how to use them correctly if I did. I guess the
real answer to my question is to take it to an emissions repair shop.

scooten94150

just buy a new 1 if its not too expensive

NGM

To put it in simpler terms.. Some of us get a lil excited with info.. Check the wiring and if there are no pinched or broken wires then replace the 02 sensor. What has happened is the heater circuit in the o2 sensor has gone bad. I would HIGHLY reccomend replacing all the 02 sensors. They are all the same age. Believe it or not it can improve your fuel mileage. Maybe not enough to notice from tank to tank, but it can improve it.

dewman

Thanks NGM, that is something I was considering anyway, replacing the O2 sensor. They run about $50-$60 each though, so that would be over $200 to replace all of them. I may just replace them one at a time, when I get the time to do it.

Bamabull

I have had the same problem. I have a 96 F150 4.9 engine. When my check engine light came on it was read as rear O2 sensor. I replaced and had the codes reset because the light stayed on. Came back on in another month and got the same reading, rear )2 sensor. Replaced again and am still getting it. Might want to go a little farther with this. That's just what is happening with mine though.