94 bonn electrical/ignition problems/codes

:banghead: I had a "check engine" light on. I bought a Super AutoScan and brought up the codes. It has numerous codes: Ignition sys failure, throttle position signal high, coolent temp sensor high, trans temp sensor high, cam shaft position sensor failure/intermittent, linear egr. I found that most of the wiring under the hood had melted and was shorting. I rewired emission, ignition, and almost every engine harness under the hood. I've replaced cam, throttle position, coolant temp, IAC, EGR, Speed, and oil pressure sending unit sensors. I've either rebuilt or replaced the pigtails. I now have a cold idle at 1500 and hot at 2000-2500 rpm (it idled ok before). I get a throttle position sensor adjustment code with the key on, engine off. I'm at a loss. One dealership says the throttle position can't be adjusted and another won't talk (just bring it in and we'll see). I had a new trans put in less than a year ago and it intermittently shifts into od, most of the time it stays in drive. Any Ideas???????????????

I think you have bad ecm

I think you have bad ecm

Michrlq,

What leads you to believe I have a bad ecm?

I replace at least 2 ecm a weak from the kind compueter you have on your car
they realy bad

He's right, it sounds like the PCM is bad. With your scanner, can you check your system voltage (battery)? not that your battery is bad, but I know when they (PCM) go bad, "sometimes" they will start running on low voltage and cause the PCM to throw wacky codes, including the tranny probs of not staying in overdrive. Just curious, but that was happening to mine, and a PCM cured it, they are nortorious for going out like Michrlq said! Good Luck!

He's right, it sounds like the PCM is bad. With your scanner, can you check your system voltage (battery)? not that your battery is bad, but I know when they (PCM) go bad, "sometimes" they will start running on low voltage and cause the PCM to throw wacky codes, including the tranny probs of not staying in overdrive. Just curious, but that was happening to mine, and a PCM cured it, they are nortorious for going out like Michrlq said! Good Luck!


Installed ECM, same problems and codes, any other ideas?

replaced the ECM, still have the same problems, any new suggestions?

Can you get your scanner, and check your system voltage? Hook it up, and note the voltage when you first start it up, then let it run for 5-10 minutes (if it will) and watch the voltage, does it drop? If it gets below nine volts, it will die eventually. Inportant note, your checking your PCM system voltage (battery feed to operated PCM), not the output from the alternator....big difference.

Can you get your scanner, and check your system voltage? Hook it up, and note the voltage when you first start it up, then let it run for 5-10 minutes (if it will) and watch the voltage, does it drop? If it gets below nine volts, it will die eventually. Inportant note, your checking your PCM system voltage (battery feed to operated PCM), not the output from the alternator....big difference.

The car will run, it is being driven every day. It is still idling at 1300 rpm cold and around 1700-2000 rpm as it warms up. The volt meter usually stays around 11-13 volts. The thing that gets me is that almost all of the sensors and wiring/pigtails has been replaced and we are still getting codes on the new sensors. Same codes as when the old sensors were in. I think I spent alot of money needlessly. What do you think?

You know, reading back at your original post, I'm kinda wondering about the integrity of your PCM Chip? Are you still using the original one as you replaced the PCM. If you shorted out some of the wiring, it couldve done something to it. I went through the same thing as you with my 94 SSEi, (as far as replacing sensors) but figured if I am going to get some mileage out of it, then "I guess" its worth it. ($$$$) but not happy about it...... Do you think you can get ahold of another computer out of a friends car, or junk yard that you could "try" and see if it stabilizes.
The PCM commands the cold idle speed until the o2 sensor can start giving an accurate signal (stays in open loop for around 30 secs) then PCM will collect data from sensors and will start controlling systems based on that data. At this point is when the "Commanded RPM" will become significantly lower, and it sounds like your is going the opposite direction "Higher". Your meter should tell you "live" what this Commanded RPM is. Also, is there a possibility you have wires crossed on the replaced pigtails? Let us know!

You know, reading back at your original post, I'm kinda wondering about the integrity of your PCM Chip? Are you still using the original one as you replaced the PCM. If you shorted out some of the wiring, it couldve done something to it. I went through the same thing as you with my 94 SSEi, (as far as replacing sensors) but figured if I am going to get some mileage out of it, then "I guess" its worth it. ($$$$) but not happy about it...... Do you think you can get ahold of another computer out of a friends car, or junk yard that you could "try" and see if it stabilizes.
The PCM commands the cold idle speed until the o2 sensor can start giving an accurate signal (stays in open loop for around 30 secs) then PCM will collect data from sensors and will start controlling systems based on that data. At this point is when the "Commanded RPM" will become significantly lower, and it sounds like your is going the opposite direction "Higher". Your meter should tell you "live" what this Commanded RPM is. Also, is there a possibility you have wires crossed on the replaced pigtails? Let us know!


We went to the parts store and asked for a pcm and we got a unit that the coil packs sit on. After reading your last input, it seems to me that we got an Ignition Control Module (icm) instead of a pcm/ecm. Are you talking about getting a new computer (electronic control module) and putting our programmable read only memory chip (prom) in the new computer and seeing if this corrects the problem? We don't think we crossed any wires as they were marked very well and were painstakingly checked to insure correctness. Let me know what you think.

These are just ideas, but not seeing the car first hand makes it difficult. You'll have to go through a Process of Elimination to try and determine what circuits are whacky, and if their is any relationship between them, that is .....do they share the same power feed.... or ground? Have you checked and cleaned all of your grounds carefully? If you are confident you got the wires back in the pigtails correctly (which sounds like you were cautious) then I would try to check the PCM as stated earlier. I went through mine with a digital volt meter and checked the connectors that plug into the PCM to see if they were running at the proper voltages, the PCM is also grounded independently to the car body under the dash (check that one too). I resolved alot of weird signals on mine by cleaning the contacts on the "All" fuses (w/pencil eraser), sounds strange but I noticed they looked discolored from heat (which was created from resistance -poor continuity) Actually eliminated a few minor problems. Last resort, instead of getting a new PCM, and re-using the PROM chip that "could" have a problem, I would try to locate another chip, or a box (PCM) with a chip in it already (number matching your chip), and swap them real quick to see if any changes are noticed. Do you know anyone at all that has model year same as yours that is working good, and could swap out the PCM temporalily? I wouldnt want to spend $$$ on a new one unless absolutely necessary.