I'm getting no low res signal at the ignition module and of course no fire. My question is: my car turns the stater and motor but I have no fire from the coil, and I noticed the security light blinks, could this keep the AC signal from going to the PCM from the Opti. I feel Imay have a bad PCM or Opti. Also on my schematics, I noticed the PCM should have a hot lead going to it at all times but it is refered to as " Ignition Feed " when Icheck for voltage it has none at the PCM plug with key in off position. When I turn key to the on position it gives me the required voltage. So I'm confused on the diagram it shows coming from the fuse " hot at all times " and calls it the " ignition feed " , should it be hot at all times or only when I turn the ignition on ? Also could the ignition switch be the problem or the PCM ? Another issue is when I turn the ignition to the on position should my Air Recirc Motor run for about two seconds ? When the car used to run I remembered a motor would come on and then stop. Maybe it was one of my cooling fans. Now I don't here it running and the engine will not fire. It just seems like the PCM maybe faulty. I tried another PCM and the results were the same.

 

Security light and air motor sound correctly working.

Have you check for codes using the on board diagnostics. If you lost the low resolution pulse completely, it would cause it not to start and should set a code 16 in module 4.

Since you are getting no AC signal at the ignition module which is pin “B” (white wire), you have no drive for the ICM and coil. BTW- that is not the low resolution pulse (from the opti), it is the drive signal from the PCM (different kind of square wave signal).

The ignition feed (12 volts) to the PCM (wire 239) is feed from the ignition switch to ECM fuse via B30 & D3 on PCM. It is hot only when the key is turned on. It is not hot at all times. I know your not using the Helms FSM book. Other documentation may have errors in them, like this one.

You say that you have tried another PCM with out success, so lets assume it is OK. Checking the low resolution pulse from the PCM can be most difficult when cranking due to its low frequency and amplitude. (Really need a scope).

An indirect alternate way to check for low resolution pulse is to check to see if the injectors are being driven by use of a nod light. If the injectors are being driven, that’s an indication the low resolution pulse is clocking thru the PCM and driving it. If the injectors are not driven, than the opti might be bad. There are other things that could be wrong like poor connections, ground, broken wire and other items that might prevent the PCM from working.