Code P1351 96 Formula

I finally got my car running after having to swap cams due to the previous owner. The car starts right up and idles right at 800-850 like its supposed to. When I took it out for a drive, it has some hesitation and its missing. As you continue to accelerate the hesitation and missing comes and goes. It will smooth out then come back again. The check engine light came on while driving and P1351 (Ignition control circuit high voltage over 4.6 volts). is the only code in the PCM. The opti, ICM, plugs, wires, and coil are all new. the ICM and coil are delphi units.

I checked the cranking volts on terminal B of the ICM and they were 1.5 volts AC, and the ground tested good. I then tested terminal B while the car was running. At idle it was 1.5 Volts ac. When you give it some gas the meter will read over 3.8 volts AC and go out of limits for a second. It then comes back and settles out at 2.5 volts at about 2000-2500 rpm. I think I found the reason the code is getting set. What would cause it to act like that?

Appears to be an intermittent open circuit. Check the white wire from the PCM pin B5 to pin B on the ICM. Make sure there is no corrosion or damage to the connector/pins on both ends of the wire. Make sure the ICM ground is good - black wire to stud on driver side head, nut is tight on stud, no corrosion. Have the ICM tested - make sure they get it good and hot. With the current quality of foreign made auto parts, the fact something is brand new and a name brand doesn't mean it can't be bad out of the box. If you have your old ICM, reinstall and see if the problem goes away.

I took the ICM off and had it tested at Autozone. I had the guy run the test three times to make sure it got hot. The ICM tested bad every time. They had one in stock, so I had them test it. The Duralast one was bad also right out the box. Luckily Delphi is going to warranty mine out for me. I checked the grounds as well, they are clean, tight, and good continuity between the connector to the ground post with only 1 ohm resistance . I checked the white wire from the icm connector to the pcm connector. It had good continuity with only about 1 ohm resistance as well. I also wiggled the wiring around while testing it.

I replaced the icm. Started it up and P1351 came back again. Im at a loss. https://uploads.tapatalk-cdn.com/201...6f116d8482.jpg

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P1351 solved! Someone tapped this wire. I followed it and it was ran in the wire bundle off the pcm. Someone must have taken their aftermarket what ever out and then left the wire bare in the loom. The voltage off of it was getting into the icm signal wire. No more code, finally. https://uploads.tapatalk-cdn.com/201...4c2223c17a.jpg

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Amazing - how were you were able to find that? Does your car have a manual fan switch? That looks like connector C100, which is the one you can tap into for a switch.

From Shoebox

http://shbox.com/1/fan_switch_wires.jpg

I just happened to notice an extra red wire soldered to the wire on the connector. Just followed it to see where it went. Ended up being bare and tucked into the middle of the harness. It didn't have any extra switches hooked up when i got it. It had a p16** code for fan 2 relay circuit in the pcm, the cooling fans work though. I also found a bunch of wiring that wasn't connected to anything under the center console.

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What a find! Great job!

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In a 96/97 C100, in addition to the 2 fan relay signal wires (dark blue, dark green), has the pink wire from fuse #11 that connects to the coil and pin A on the ICM connector. Somebody really hacked it up.