Initially, my car would run then die and will not start up until it cools off.
I took apart the old opti and it looks like it was dunked in salt water.

Car starts up fine now with the new Accel opti. The GM one was not available at the time from summit so I thought I'd give it a try.

Now I'm getting the DTC P1351 and on occasion if idling it will die. However, I can start it up immediately after unlike before.

I used an external wire to confirm a good connection with the white wire from the ICM to the PCM and still have the same problem. Getting 2.xx volts from white wire constantly when cranking. Lamp test on C terminal to B+ and lamp comes on bright.

ICM and Coil are new.
The optispark wire harness is also new from Caspers Electronics.
Plug Wires are new as well. Spark plugs are kind of old but I have another set waiting to go in, hopefully, next week.

Could it be the opti is bad out of the box?

 

P1351 sets based on voltage to the IC module exceding 4.61V, indicating an open circuit. Appears you may have an intermittent wiring problem.

People have had lots of problems with the ACCEL Optis, and they are not recommended. But this appears to be a different problem.

 

Should I remove the white wire completely instead of using an external wire in conjunction with the white wire to test?

In my search I've read a bad alternator could also make the pcm throw codes. Could that also be a possibility in my case eventhough it's throwing the same code constantly? Just trying to cover all bases in case one thing will make the pcm throw wrong codes. Kinda like the time my reverse was locked out and it turns out one of the wires to the maf was grounding out.


Thanks

 

The post back in November dealt with OBDI codes for the opti. See here:
https://www.camaroz28.com/forums/sho...d.php?t=721304

Now you're posting OBDII codes.

So are we to take it that you switched PCM's?

So did the OBDI pcm give you a 41 right before you switched to the OBDII PCM?

Is that why you switched?

Let's not forget you bitched about the "white" IC wire back in June. See here:
https://www.camaroz28.com/forums/sho...72#post6000072

So it would appear you switched OPTI's against advice and PCM's and where are you now? Right back were you started from.

Can we now take a more methodical approach to figuring out what the problem could be or do you have more parts to try?

 

I'm switching everything back to stock to eliminate any faulty modified items. Also switching back to obdii codes allows me to follow my factory manual troubleshooting page.

Changing out the opti made it possible for the car to start right up again if it dies. It does not die all the time now just misfires.

I've read on many threads where the problem with p1351 was fixed by changing the ICM. Since my friend works at an autoparts store he was able to get me one at a deep discount. So it seemed the logical step since the icm and coil has 130k mile on them.

Hopefully, next week I'll have time to disconnect the white wire completely and run an external wire and see how that goes. It's been a while since I took a GM pin out but if I remember correctly it comes out by pressing down from the front right?



Thanks

 

If the old one is a problem, leave it there and add a second one back probed in with it. Won't hurt anything.

 

I did that already as stated in the first post. Still got the same problem.

I'm thinking maybe it's making contact with another power source intermittenly so I'm going to disconnect it from both ends and run an external wire to see if it makes a difference.

Is the reading from the white wire suppose to fluctuate from 1-4 volts? I'm only getting a constant 2.xx volts ac.

 

Disconnected the white wire from the pcm and ran a wire to the icm. I wasn't able to disconnect the white wire from the icm w/o cutting it so I left it on. The started up fine and looked promising. Few minutes of idling and it died on me once again. This time no SES light and no DTC recorded.

Should there be any voltage reading on the white wire after the car has started?
I will try again tomorrow and see if I can get a DTC.

 

The ICM is an amplifier, when inactive the white wire sits at 4.6v, but when the PCM sees the opti low res pulse, the PCM modifies the pulse timing and then sends a 0.5v pulse on the white wire. The .5v pulse on the white wire is power amplified within the ICM and the ICM output on pin D is driven to ground to fire the coil. Therefore the wire should be at 4.6 volts with 0.5V pulses when running. This would read a a lower AC voltage on a multimeter. Buy the way the DTC only sets while cranking, if the wire fails when running the car will just stall. The DTC also means two things the wire was not at 4.6 V when the PCM was not commanding a spark (being held to ground) - Or - the wire was not a 0.5 v when PCM commanded spark (open circuit) . To set the DTC these conditions must be present for 42 low res pulses while cranking. So a very noisy defective low res pulse from the opti could also cause this failure buy the PCM thinking the static noise is 42 pulses. Also If you did not disconnect the white wire from the ICM side then it still could be pulling the circuit to ground. The white wire has a splice in the harness about 2 inches from the #3 injector you could check for problems there. Also put a multi meter set for ohms between white wire and ground, wiggle the harness to see if it changes. Make sure the black wire ground is good by checking the ground stud on the front of the left head, both the coil and ICM are grounded on the black wire on that stud. W/ign on the pink wire should be steady +12 while wiggling the harness. And the dark green to the coil s/b at +12V at that time. If you touch the white to ground pin D should go to ground and fire the coil.

 

Thanks bobdec. I'll check again recheck and post my results.

A co-worker said he had the same problem and after spending $1800 at GM they found it was a $10 part that was bad. He said it looked like a capacitor that's mounted close to the coil. This was on a LT1 vette. The only thing I see by the coil is the ICM. Were the obd1 lt1 vettes that different from ours?

Out of all the searches I've done for the DTC P1351, no one has really solved the problem or post a solution. Seems like most people ended up selling their car. Hopefully, I'll be able to post a solution.

 

Did he have a 92/93? They had a filter on tach signal from the coil. The 94's deleted that, taking the tach signal from the PCM.

 

I'll have to check with him again tomorrow. I thought he said 94 but I might be getting it confused with his son's camaro.

Now that you mention the tach, I notice when the car misfires even when I'm pumping the gas the tach will drop to 0rpm then jump back up to the correct rpm. Does that mean anything?

 

Confirmed my co-worker's corvette was a 94.

His son had a 93 camaro and at around 130k miles it started misfiring as well. He found it was oil that kept fouling up the plugs causing it to misfire. He sold it for less than $2k.

 

Turns out car was stalling due to a bad Accel Opti out of the box.
Replaced with a GM performance Opti and car no longer stalls.
Hope this info helps someone in the future.

 

I had an Accell opti and it was crap. It cause misfires and hadsparks shooting out of the cap and into the water pump. Even the pulse wheel was rubbing the optical sensor making a rubbing noise.

Avoid it like AIDS.