ASD relay no PCM ground

Okay. Just to make sure I am on the same page. The PCM is not grounding the ASD? Plain and simple correct?

The PCM is responsible for getting the ignition switch change and it then grounds the ASD as this is what powers the injectors. So basically fuse 2 in the PDC supplies 12 volts to the relay through pin 30 and 85. When the PCM wants the ASD closed, start and engine running, the PCM closes the ASD by grounding pin 86.

This will close the relay and send voltage through pin 87 to the injectors and back to the PCM telling the PCM that the ASD is closed.

This code is most likely related so I would suggest addressing the code or do the testing to find out what the issue is.

More then likely it is the PCM but it could be wiring so we need to run through the testing below.

Here are a couple guides that will help with this:

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Please find the info below and let us know what you find or questions.

Thanks

Lets start with the ASD relay. The Engine Computer grounds that terminal 86 at two times. The first is for one second when the ignition switch is turned on. Next, it gets turned on again when the computer sees engine rotation, meaning cranking or running. On older models, it knows that by the presence of signal pulses from the crankshaft position sensor and the camshaft position sensor. Both signals were needed for the engine to start and run. If one signal was lost while running, the engine would stall and not restart.

Around 2002 this changed on some models. You still needed both signals for the engine to start, but if a sensor failed while the engine was running, it would continue to run until it was stopped, then it wouldn't restart. I've never done this myself, but another person posted a similar series of events that you've done with grounding the ASD relay. It sounds like your engine will run in back-up mode on just one sensor, but the computer needs to see both signals to turn on the ASD relay.

There's two observations that will tell if this is correct. The first is the ASD relay should still be turning on for one second when you turn on the ignition switch. If you hear the hum of the fuel pump, that is proof this circuit is working. If you can't hear it or aren't sure, the best test is to measure the voltage at any place 12 volts appears from the ASD relay. That includes any injector, any ignition coil, or either smaller terminal on the back of the alternator. Look for the wire that is the same color at each of those places. That's usually a dark green / orange wire and is shown in the second diagram. A test light is the best choice for this. Most digital meters don't respond fast enough. You should see a bright test light for one second when you turn on the ignition switch. If you do, we're done with the ASD relay circuit. It's working and the computer has control of that relay

Next, observe if the test light turns on when you crank the engine. If it does not, the signal is missing from one of the two sensors. With a failed sensor and an ASD relay not turned on, you'll have no spark, no injector pulses, and no fuel pump. This accounts for about 95 percent of crank / no-starts. What can be misleading is you'll still have normal fuel pressure due to that one second the fuel pump relay turns on each time you turn on the ignition switch.

If the ASD relay does turn on during cranking, (which yours isn't), and you have a no-start condition, it has to be due to a dead ignition system or a dead fuel pump, but not both. Those two systems account for the other five percent of crank / no-starts.

Let me know what you find with these observations. If it looks like a sensor has failed, we're going to need a scanner to see which circuit needs to be diagnosed.

Hi KASEKENNY1. I'll wait to see if you need me to add any comments.

Just to be clear, you replaced the PCM for this issue or was it another issue? Was this issue there when you installed the PCM?

Either way, if it were me at this point I would be putting a PCM in it.

As stated above, the ASD is grounded as soon as there is engine rotation. So these engines will start on just the cam sensor if it rotates enough to learn the position.

So it looks like the PCM is where I would be going.

Keep us updated and let us know what you find with this.

Thanks

Please allow me to add one comment for your consideration, There are always multiple 12-volt feeds to a computer. Almost all Chrysler Engine Computers use four of them. I added arrows to them in these drawings. The fourth one's description is confusing. Once the computer turns on the ASD relay, along with feeding the ignition coils, injectors, and alternator field, another line runs back to the computer on that dark green / orange wire to verify the relay got turned on. That circuit is also the source for the voltage regulator where it runs the alternator's field control circuit. The description means the output of the relay is feeding terminal 12 in connector C3. You might want to verify the other three 12-volt inputs are there.

Oh. I am sorry. I didn't understand that. In that case I agree with CARADIODOC.

Let us know what you find. Thanks again.