E38 stand alone harness --During scanning, starter shuts off scanner

[blindsquirrel]

1. Ignition OFF, disconnect the harness connector at the crankshaft position (CKP) sensor.
2. Test for less than 1 ohm between the CKP low reference circuit, terminal B, and ground.
⇒ If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
3. Ignition ON, test for 4.8-5.2 volts between the CKP 5-volt reference circuit, terminal C and ground.
⇒ If less than the specified range, test the 5-volt reference circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the ECM.
⇒ If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
4. Ignition ON, test for 4.8-5.2 volts between the CKP signal circuit terminal A and ground.
⇒ If less than the specified range, test the signal circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the ECM.
⇒ If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
5. Ignition OFF, connect a fused jumper wire to the CKP signal circuit terminal A.
6. Ignition ON, momentarily touch the other end of the fused jumper wire to the battery negative post. The CKP Active counter, should increment.
⇒ If the CKP Active counter increments, test or replace the CKP sensor.
⇒ If the CKP Active counter does not increment, replace the ECM.

Keep in mind this is taken from the 2009 manual, I really highly suggest that you get your own service manual. Just because it's an aftermarket harness does not mean you can fix it without the manual.

[Lakegoat]

Thank You !!!
I can tell by reading the tests that I will be getting a new ECM

[blindsquirrel]

Meaning, you already checked the CKP signal wire integrity with both ends unplugged, and verified it's going to the correct ECM pin?

[Lakegoat]

No, That was just me guessing it was going to be the ecm. I have checked the 5 volt reference previously, so that was my "feeling". Can't figure out why the cam sensor quit counting on the last log. #^%^&*&^%&^$$

[Lakegoat]

Disconnected the crank sensor plug from sensor
Test#2= .5 ohms---bad ecm
Test#3= 5 volts---bad ecm
test#4= 5 volts--- bad ecm
I guess that verifies it

[blindsquirrel]

So now CKP 'A' has 5v? And when you checked it previously it had .1-.2v?

Did you do step 6 while watching in the scanner or are you just hankerin' to put an ECM in it because reasons?

[gtstorey]

Disconnected the crank sensor plug from sensor
Test#2= .5 ohms---bad ecm
Test#3= 5 volts---bad ecm
test#4= 5 volts--- bad ecm
I guess that verifies it

If your test # is referring to the step #, it looks to me like the values are within range. This means move to the next step. The "if the circuit tests normal, replace the ECM" refers to testing circuit if the values are out of range.

[blindsquirrel]

I do not have high confidence that any of this is being tested in a reliably precise fashion.

[Lakegoat]

OUCH!! Thanks for the vote of non confidence.
Let's look at this: (3. Ignition ON, test for 4.8-5.2 volts between the CKP 5-volt reference circuit, terminal C and ground.
⇒ (IF)less than the specified range, test the 5-volt reference circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the ECM.)
First thing, Ignition ON---Check terminal C for 4.8 to 5.2 volts-------IF the circuit tests normal, (it tested 5v) replace the ECM. It also states (IF) less and (IF) more, check the 5volt ref circuit. However, it was not less or more than 4.8 to 5.2v----so where do you see that it says go to the next step. I put the steps that I checked, how many have to come up bad according to your list ?? No. I didn't check the #6, why would I. Are you saying that the other three tests don't mean anything?

[gtstorey]

My experience reading GM service manuals, which is more than some and a lot less than others, says the steps are saying that to check voltage/resistance and if the measurement is not what is expected, you check the circuit (the wires) between the ECM and the measurement point. If the circuit (wires) check out good, that means the ECM is responsible for the bad reading. If the voltage/resistance measurement checks good, there is no need to check the circuit (wires) because ithe ECM is doing what it is supposed to.

I’ll be the first to admit that these things aren’t always written clearly. If you have experience reading GM diagnostic steps and feel that my interpretation is wrong, go ahead and replace the ECM. I will add that for it to fail multiple steps, the ECM would have to have multiple failure’s which would be very rare, especially if every other circuit in the ECM seems to be working.

[blindsquirrel]

Is voltage between 4.8 and 5.2 volts?
If YES, go to next step.
If LESS than 4.8 volts, is the wire shorted to ground, or open? If yes, fix the short to ground or open. If no short to ground or open is found, replace ECM.
If MORE than 5.2 volts, is the wire shorted to voltage? If yes, fix short to voltage. If no short to voltage is found, replace ECM.

The obvious question is this: It at one time had no voltage on CKP pin 'A' signal wire, and it also had no RPM reading. But it now has 5v on pin 'A' - does it now have RPM reading? Did it start working when the status of that signal wire changed? And, what else changed when the voltage on that wire changed? Is there a poor pin fit at the PCM? Damaged wire somewhere between ECM & sensor? Or was it a faulty test and it really had 5v the whole time?

[Lakegoat]

Is voltage between 4.8 and 5.2 volts?
If YES, go to next step.
If LESS than 4.8 volts, is the wire shorted to ground, or open? If yes, fix the short to ground or open. If no short to ground or open is found, replace ECM.
If MORE than 5.2 volts, is the wire shorted to voltage? If yes, fix short to voltage. If no short to voltage is found, replace ECM.

The obvious question is this: It at one time had no voltage on CKP pin 'A' signal wire, and it also had no RPM reading. But it now has 5v on pin 'A' - does it now have RPM reading? Did it start working when the status of that signal wire changed? And, what else changed when the voltage on that wire changed? Is there a poor pin fit at the PCM? Damaged wire somewhere between ECM & sensor? Or was it a faulty test and it really had 5v the whole time?

Thanks for all your help.
When I posted that one pin had .1 to .2 volts---that was with plug installed on the sensor and cranking the engine over. So the result was the low voltage signal output by the sensor. It was not unplugged and not as specified in the test list above. It has always had 5v on both pins with it unplugged and not cranking. I don't understand why you post a GM troubleshooting list that is specific on what to do, and now you want to change what it actually says. I will check the #6 test today and post results. I don't want to buy another ecm, pay more credits, waste time, but when it says on 3 tests to replace the ecm ???? The wires from the sensor plug---5v to pin 2 on X1, Ground to pin 69 on X1, Signal to pin 68 on X1 are where they are supposed to be and have been continuity checked.

[blindsquirrel]

Dude. I already told you I do not even have service manuals to cover a 2012 anything. YOU NEED YOUR OWN MANUALS.

What am I changing about what it says? I paraphrased it to explain how their wording works, which you weren't getting. They used to use charts like this:

screenshot.21-09-2023 03.52.52.png

Despite the change in format/language, you still follow it the same way.

[blindsquirrel]

but when it says on 3 tests to replace the ecm ????

It does not say that. Not for what you claim your measurements are. Only if the voltages are NOT correct, and a wiring problem has been ruled out, THEN replace ECM.

[blindsquirrel]

#2: 1 ohm or less = PASS, DO NOT replace ECM, go to #3.
#3: 4.8-5.2 volts = PASS, DO NOT replace ECM, go to #4.
#4: 4.8-5.2 volts = PASS, DO NOT replace ECM, go to #5 & 6.

[gtstorey]

BlindSquirrel is one of those I'm talking about with way, way, way more experience reading GM service manuals than me. Unless you have a huge amount of experience reading GM service manuals, listen to what he is telling you.

Starting with looking up the test procedure for your particular model on Alldata. Yes, it will cost you a few bucks and it will likely be the same test. Good chance it will be written a slightly different way.

[Lakegoat]

Thanks Dude

[gtstorey]

Last attempt.
The resistance isn't greater than specified value. No reason to test the circuit. I can admit that I see why you are reading it the way you are. If you can't see why we are reading it the way we are, then we can't help you and go ahead and buy the ECM.

[Lakegoat]

Last attempt.
The resistance isn't greater than specified value. No reason to test the circuit. I can admit that I see why you are reading it the way you are. If you can't see why we are reading it the way we are, then we can't help you and go ahead and buy the ECM.

Thank You.
Not purchasing ecm yet. As soon as I get my rotor pack back, I can go ahead and see if it starts and runs. Alvin might be correct in the way the harness is wired. I just can't find anything wrong with it up to this point. I have tried to check everything that was posted. I have no way to know that something means PASS when it does not say that anywhere.

[gtstorey]

Thank You.
Not purchasing ecm yet. As soon as I get my rotor pack back, I can go ahead and see if it starts and runs. Alvin might be correct in the way the harness is wired. I just can't find anything wrong with it up to this point. I have tried to check everything that was posted. I have no way to know that something means PASS when it does not say that anywhere.

It takes experience reading the diagnostic steps. GM changes how they are written all of the time. I preferred the decision tree style posted in #33, but for some reason, GM moved away from that.