Anybody here familar with diagnosing failed PCMs??
04-20-2013, 04:20 PM
#1
Member
Thread Starter
Anybody here familar with diagnosing failed PCMs??
To simplify this I will move the posts from the engine forum over here to this thread
Original thread title
93 Suddenly barely runs, check engine light on
Original post
My 93 which has never shown a CEL suddenly out of the blue on a start yesterday morning will barely run. This truck has had real light duty for the last decade basically only running 10 miles to the dump with trash bags weekly and a friend of mine using it weekly to go to the store and see his doctor once in a while. Recently I have had the opportunity to get on some nice hardwood 10 miles away and have been hauling green wood (about 20 loads) back to the house to replenish the firewood for next winter and beyond. The truck has been handling this duty like a champ, running strong and smooth with FULL loads.
Due to that information I think what has failed must be electrical as it was fine as wine, then overnight it is stumbling all over itself barely running until you give it throttle, but then it is still rough. It it was the fuel filter I would have noticed an issue with full loads recently, the pumps both power up normally and switching tanks has no effect on the problem, so I do not suspect fuel pressure or supply as what changed overnight.
I have checked the battery and alternator, both are performing normally. I have 12.8 volts before startup, voltage at the battery rises to 13.7-14 volts when running. Truck remains running when battery is disconnected while running, different battery also gets same results. I have checked the codes and I have about 18 different ones. All of the codes but one refer to a circuit failure or a sensor returning a lower than expected voltage, the one which stands out is code 513. This code in my alldata account is described as such "PCM Int Voltage Failure KOEO". I am afraid that means something has failed in the trucks computer which is preventing all of these other control circuits from getting any, or sufficient, voltage to operate. In the factory service chart that code has only 1 action to perform, Replace PCM. I am going to remove the PCM and attempt to investigate it. My question to the knowledge base here is, has anyone here had any luck replecing the ICs in the computer to repair it? The reason I ask is I am currently unemployed and cannot spend a dime unless I absolutely have to. I have found a PCM online at Auto Parts Warehouse for $101.00, but if I can replace the ICs for 10 dollars I would rather do that at the moment.
Thanks in advance
Post 2
Well after inspecting the PCM, none of the ICs or transistors are mounted in sockets, so it does not look like replacing any ICs at home will be easy or worth the time.
Has anyone had an issue where a sensor or component has failed and caused the PCM to fail?
If so what sensor or component would need to be verified before I put the replacement PCM in the truck, I certainly dont want to buy one only to watch it get "eaten" by something else.
Post 3
After looking closely at the possible Cardone PCMs at the Auto Parts Warehouse site I finally saw the difference in all the PCMs with the different prices (9 of them). They referred to a four digit code and whether the vehicle was auto or manual, of course mine would have to be the most expensive one at $211, code F3TF and an automatic transmission.
Off to search for a cheaper one......
Post 4 by tvand13
"Someone much more experienced than me will have to confirm this, but is is possible it could be something like a ground to the computer? "
Post 5
It is possible the PCM may not be bad I would imagine, I have been searching my alldata account for a procedure or way to verify the PCM has failed other than the code 513 that was reported.
On some of the other codes I followed the troubleshooting procedure back to the point where I am instructed to install a breakout box to verify PCM failure, but I do not have one of those atm.
The connections and connectors are fine as I inspected them as I removed the PCM and also checked the large harness connectors at the firewall.
Since I do not have a breakout box, I cannot measure PCM pins while it is installed in the vehicle but I may be able to use the wiring harness info to find a way to check the same signal further down the wire/s. I was unable to find the way to check the PCM reference voltage transistors with it outside the truck with my multimeter using the Ohm or diode check function, but I think I should be able to do so, I just am not sure what pins and what values to check for in order to verify that transistor/s have opened up.
Post 6
For reference here are the codes that were retrieved earlier.
I removed the battery last night and left the cab light switch on to clear codes that may be old/unrelated, even though this is the first time the check engine light has come on since I bought this truck new.
I restarted the truck and let it run for about a minute idling and revving up to 1500 or so, then installed the jumper and read these codes below.
112- IAT sensor less than minimum voltage
117- ECT sensor less than minimum voltage
122- TP sensor less than minimum voltage
126- MAP/BARO higher or lower than expected
327- EGR below minimum voltage
513- Int Voltage failure KOEO
552- Secondary Air Injection Bypass circuit failure KOEO
556- Fuel Pump relay primary circuit failure
558- EGR vacuum regulator circuit failure
621- Shift Solenoid 1 circuit failure KOEO
622- Shift Solenoid 2 circuit failure KOEO
624- Electronic Pressure control circuit failure
626- Coast Clutch Solenoid circuit failure
629- Torque Converter Clutch solenoid circuit failure
631- Transmission Control Indicator lamp circuit failure KOEO
638- Transmission Oil Temperature sensor circuit below minimum voltage
654- Manual Lever Position sensor indicating not in nuetral during self test
Post 7
I just cleaned up the two grounds that show being used by the PCM, they seemed in good shape.
I hate to buy a part just on a code without confirming the part is bad another way, especially parts that cost more $40.00, but usually there is a procedure to follow in the factory service manual first, that code 513 just says replace PCM. I am going to keep trying to check to see if there isn't a failed relay or solenoid loading down that voltage and causing all of these issues, maybe also tricking the PCM into thinking it has an internal failure. I think I am going to have to find a way to borrow or buy a breakout box for the 60 pin Ford EEC IV PCM though
Original thread title
93 Suddenly barely runs, check engine light on
Original post
My 93 which has never shown a CEL suddenly out of the blue on a start yesterday morning will barely run. This truck has had real light duty for the last decade basically only running 10 miles to the dump with trash bags weekly and a friend of mine using it weekly to go to the store and see his doctor once in a while. Recently I have had the opportunity to get on some nice hardwood 10 miles away and have been hauling green wood (about 20 loads) back to the house to replenish the firewood for next winter and beyond. The truck has been handling this duty like a champ, running strong and smooth with FULL loads.
Due to that information I think what has failed must be electrical as it was fine as wine, then overnight it is stumbling all over itself barely running until you give it throttle, but then it is still rough. It it was the fuel filter I would have noticed an issue with full loads recently, the pumps both power up normally and switching tanks has no effect on the problem, so I do not suspect fuel pressure or supply as what changed overnight.
I have checked the battery and alternator, both are performing normally. I have 12.8 volts before startup, voltage at the battery rises to 13.7-14 volts when running. Truck remains running when battery is disconnected while running, different battery also gets same results. I have checked the codes and I have about 18 different ones. All of the codes but one refer to a circuit failure or a sensor returning a lower than expected voltage, the one which stands out is code 513. This code in my alldata account is described as such "PCM Int Voltage Failure KOEO". I am afraid that means something has failed in the trucks computer which is preventing all of these other control circuits from getting any, or sufficient, voltage to operate. In the factory service chart that code has only 1 action to perform, Replace PCM. I am going to remove the PCM and attempt to investigate it. My question to the knowledge base here is, has anyone here had any luck replecing the ICs in the computer to repair it? The reason I ask is I am currently unemployed and cannot spend a dime unless I absolutely have to. I have found a PCM online at Auto Parts Warehouse for $101.00, but if I can replace the ICs for 10 dollars I would rather do that at the moment.
Thanks in advance
Post 2
Well after inspecting the PCM, none of the ICs or transistors are mounted in sockets, so it does not look like replacing any ICs at home will be easy or worth the time.
Has anyone had an issue where a sensor or component has failed and caused the PCM to fail?
If so what sensor or component would need to be verified before I put the replacement PCM in the truck, I certainly dont want to buy one only to watch it get "eaten" by something else.
Post 3
After looking closely at the possible Cardone PCMs at the Auto Parts Warehouse site I finally saw the difference in all the PCMs with the different prices (9 of them). They referred to a four digit code and whether the vehicle was auto or manual, of course mine would have to be the most expensive one at $211, code F3TF and an automatic transmission.
Off to search for a cheaper one......
Post 4 by tvand13
"Someone much more experienced than me will have to confirm this, but is is possible it could be something like a ground to the computer? "
Post 5
It is possible the PCM may not be bad I would imagine, I have been searching my alldata account for a procedure or way to verify the PCM has failed other than the code 513 that was reported.
On some of the other codes I followed the troubleshooting procedure back to the point where I am instructed to install a breakout box to verify PCM failure, but I do not have one of those atm.
The connections and connectors are fine as I inspected them as I removed the PCM and also checked the large harness connectors at the firewall.
Since I do not have a breakout box, I cannot measure PCM pins while it is installed in the vehicle but I may be able to use the wiring harness info to find a way to check the same signal further down the wire/s. I was unable to find the way to check the PCM reference voltage transistors with it outside the truck with my multimeter using the Ohm or diode check function, but I think I should be able to do so, I just am not sure what pins and what values to check for in order to verify that transistor/s have opened up.
Post 6
For reference here are the codes that were retrieved earlier.
I removed the battery last night and left the cab light switch on to clear codes that may be old/unrelated, even though this is the first time the check engine light has come on since I bought this truck new.
I restarted the truck and let it run for about a minute idling and revving up to 1500 or so, then installed the jumper and read these codes below.
112- IAT sensor less than minimum voltage
117- ECT sensor less than minimum voltage
122- TP sensor less than minimum voltage
126- MAP/BARO higher or lower than expected
327- EGR below minimum voltage
513- Int Voltage failure KOEO
552- Secondary Air Injection Bypass circuit failure KOEO
556- Fuel Pump relay primary circuit failure
558- EGR vacuum regulator circuit failure
621- Shift Solenoid 1 circuit failure KOEO
622- Shift Solenoid 2 circuit failure KOEO
624- Electronic Pressure control circuit failure
626- Coast Clutch Solenoid circuit failure
629- Torque Converter Clutch solenoid circuit failure
631- Transmission Control Indicator lamp circuit failure KOEO
638- Transmission Oil Temperature sensor circuit below minimum voltage
654- Manual Lever Position sensor indicating not in nuetral during self test
Post 7
I just cleaned up the two grounds that show being used by the PCM, they seemed in good shape.
I hate to buy a part just on a code without confirming the part is bad another way, especially parts that cost more $40.00, but usually there is a procedure to follow in the factory service manual first, that code 513 just says replace PCM. I am going to keep trying to check to see if there isn't a failed relay or solenoid loading down that voltage and causing all of these issues, maybe also tricking the PCM into thinking it has an internal failure. I think I am going to have to find a way to borrow or buy a breakout box for the 60 pin Ford EEC IV PCM though
Last edited by wb22rules; 04-21-2013 at 12:18 AM. Reason: Moved thread from engine forum to here
04-20-2013, 07:07 PM
#4
Senior Member
I`m banking on bad grounds or computer. Yank out the computer and smell it. If it smell burnt just get a new one. Some people try to fix them. Not sure how they do it. Although someone else had a something frying computers not long ago. And your right about pin 60. It only gets tested though a breakout box.
04-20-2013, 11:51 PM
#5
Member
Thread Starter
Thanks for the replies
I inspected the computer, all looks great visually and no "electronic death smell" , but with that thick layer of waterproofing on all of it I am not sure the elec death smell could escape. I have spent the last 20 years making a living fixing low voltage electronic systems so I know what to look/smell for, but I also know that any electronic component can fail at any time and look perfect as well.
I will check out/clean the other grounds tomorrow, but the truck is not messed up from salty roads or winter driving, for its age I would say it is better than most corrosion wise.
I inspected the computer, all looks great visually and no "electronic death smell" , but with that thick layer of waterproofing on all of it I am not sure the elec death smell could escape. I have spent the last 20 years making a living fixing low voltage electronic systems so I know what to look/smell for, but I also know that any electronic component can fail at any time and look perfect as well.
I will check out/clean the other grounds tomorrow, but the truck is not messed up from salty roads or winter driving, for its age I would say it is better than most corrosion wise.
04-21-2013, 12:04 AM
#6
Member
Thread Starter
I am pretty sure its electronic by the way it happened in an instant, and by the fact that the truck went from having no CEL on ever, to having 18 codes, all which indicate low voltage or complete circuit failures.
Last edited by wb22rules; 04-21-2013 at 12:20 AM.
04-21-2013, 03:10 AM
#7
Senior Member
I can find nothing other than disconnected grounds or wiring harness that would cause that many failures other than pcm failure. One test you can try is test a sensor for reference voltage from the pcm. No 5v reference, bad pcm assuming the circuit is in tact. According to my instructor there is no 2 ways about that.
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04-21-2013, 10:29 PM
#8
Member
Thread Starter
I can find nothing other than disconnected grounds or wiring harness that would cause that many failures other than pcm failure. One test you can try is test a sensor for reference voltage from the pcm. No 5v reference, bad pcm assuming the circuit is in tact. According to my instructor there is no 2 ways about that.
Now it is possible I may have caused my own problem by using my tailgate to clamp down some metal that I was welding on with my MIG welder a few weeks before this problem appeared. Rest assured I will not be welding on my tailgate anymore even though 2 weeks passed between the welding and this issue, just in case that was what caused it.
04-21-2013, 11:11 PM
#9
Senior Member
Its been said that you are to disconnect the battery cable when welding on vehicle. I never have and haven't had any problems. Have you tried searching at local junkyards for a PCM. What engine and transmission do you have and is there emissions testing in your area. If not you can use a different pcm as long as it matches your engine and tranny. As you have searched for PCMs you have probably noticed there are ones for federal emissions, high altitude emissions and California emissions
Last edited by jrh5610; 04-21-2013 at 11:16 PM.
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wb22rules (04-22-2013)
04-22-2013, 10:01 AM
#10
Member
Thread Starter
Its been said that you are to disconnect the battery cable when welding on vehicle. I never have and haven't had any problems. Have you tried searching at local junkyards for a PCM. What engine and transmission do you have and is there emissions testing in your area. If not you can use a different pcm as long as it matches your engine and tranny. As you have searched for PCMs you have probably noticed there are ones for federal emissions, high altitude emissions and California emissions
Mine is a F3TF and the last two letters are VA
The only one I could find that matches that online stated it was for a manual transmission. The ones that start with F3TF and that are for the E4OD trans that I think I have end with ZA, so I am not absolutly certain if I should match the numbers and get the VA assuming the description is wrong, of if I should get the ZA which probably meets a different emissions standard as you suggested.
If I go to a pick a part junkyard and get one from 93 with a straight six and the trans with the OD I should be fine though, no matter if the id doesnt match exactly ?