03 Silverado 4.3L A.T. P0315 no start new ECM

I would like to say first I am glad to be here.

Trying to be a good neighbor and friend, I took on my neighbor's truck in after a few other things that have been done to it and have been unsuccessful. I'll upload my notes since most is explained there but here is an overall picture.

Crank no start with a hard P0315. Came in with new (remanf) ECM and I am trying to do the learning procedure per the ECM company and no good results. Their initial procedure is install ECM, connect battery, crank for a few secs until security light comes on, leave key on for 20 min, turn off for 1 min, crank again until light comes on again, leave key on for another 20min, repeat process 4 to 6 times and in should be ok. Erase any DTC's and done.

Followed the procedure, used my timer app on phone to come back to truck accordingly and did this a few other times. I found another procedure for similar GMC vehicles and it goes like this, crank and security light should come on, leave key on for 11, turn off for 30 sec, key on for another 11min, repeat 5 times, last time key is on the security light should turn off and crank to start. Erase DTC's and you should be good to go. NO good results either.

I called the ECM company; I talked to a technical advisor and he sounded a little upset that I walked away during the 20min count down but yet I think I followed procedure with the stopwatch. He advised, ignore our handout, ignore the 20min and stay with the truck 100% during process. They issued a new ECM because I mentioned the security light will not turn off at all now. He mentioned it went into safe mode and locked itself out. Do their same process but turn key off right after security light turns off, leave off for 30 min, and repeat 4 to 6 times and this should fix it. He mentioned there is a 15 sec window to turn key off after the security light turns off. Did this word per word and no good result.

All this time I am doubting the previous fix and see DTC P0315. I start diagnose and the rest is in my notes. Please advise..

Tools at my disposal to diagnose, average scanner, test light, multimeter, and any hand tool needed for the job. I work out of my garage and mainly do work for all my vehicles and a friend or two. I never take on a repair job for money; I don't like to. I like to keep this as a hobie but this one is really kicking my butt.

Thank You Ahead of time.

As you can see in my notes, I did a few other searches on the truck not related to P0315 mainly to keep me busy and try to find out why the new ECM was installed. At work (R&D) or in anything I do I try to understand why someone else did what they did. Most times it makes sense; sometimes I just can't figure out.

Anyway, thank you!

The procedure I have had success with is close but not quite the same.
I don't follow the time guide lines so strictly. More of a guide, not such a rule.
It does take about 30 minutes, and sometimes doesn't take the first time around.
1) turn the key to the "on" position. Not crank. Cranking the engine resets the whole procedure.
The theft lamp will be illuminated. Leave the key on until it goes out (about 10 minutes).
2) once the theft lamp goes out, turn the key to the "off" position for about 5 seconds. Do not remove the key from the ignition.
3) turn the key to the "on" position again, being sure not to crank the motor. The theft lamp will again be illuminated. Leave the key on until the theft lamp goes off (about 10 minutes).
4) turn the key to the "off" position for about 5 seconds, being sure to not remove the key from the ignition.
5) turn the key to the "on" position, do not crank the motor. The theft lamp will be illuminated. (If at this point the lamp goes on and comes right back off, you're done. The car should now start and run. I've had very few take after only 2 cycles, but it's not unprecedented) Wait for the theft lamp to go out (about 10 minutes).
6) turn the key off for about 5 seconds, do not remove the key.
7) at this point, (after 3 ten minute on Off cycles with no cranking and having not removed the key) when you turn the key on again, the theft lamp should go on, then off. This signals that the relearn has been successful. Now the car should start and run.

Like I said, it sometimes takes a couple tries, so leave yourself plenty of uninterrupted time. I set my phone timer for 9 minutes then go back to the car and watch for the theft lamp to turn off. I use the lamp as more of an indicator than time.

Hope this helps you out!

And welcome to the forum! I for one appreciate a thorough, well put together post like yours with all the vehicle information and tested performed! Didn't look at your notes though, hard to see on my phone. Should be on the PC tomorrow.

There may be a data pid available on your scan to that will show something to the effect of "fuel enable/disable"
Disable obviously means the anti theft system is cutting the fuel.

You may have greater success with the relearn procedure if you disconnect the battery for a few minutes before you begin just to get all the codes out of all the modules.

Thanks, I will try your procedure by I am cautious about trying any procedure again without being sure of a few things.

All the gauges on the dash are off, over limited. Owner claims they have been this way for a while even while the truck was working. Although it isn't my first chevy I see this way. IT is a common issue with these models. There is even a guy I know that is dedicated to fixing gauge clusters. Question is:
Does this affect the relearn procedure?

See my results from the CPS. Since I don't have an oscilloscope or I can't graph my outputs, I turn the engine manually and monitor the outputs. I should see voltage drops to 0V three times in 360deg. I do but only for a split second. I know the window is not small. I rotate to the next window and I leave it there to see if the voltage will stay at 0V. It doesn't; it goes back up in a split second. I was curious, so I removed the CPS and at first glance I noticed some rubbing on it. I continue to connect directly to the battery with jumpers to monitor voltage. It works as I think it should; It reads over 12V near metal and 0V as I move it away from metal but only for 5sec or so. It goes back up to 12V.
Is this normal to go back up to 12v even at the window? Do they have a built in switch with a small cap or something to keep it there for a split sec. IF so, was I only reading a split sec with the multimeter because I was helping with the discharge by adding a little more load while pluged in?

I'm concerned about the rubbing though. I fixed this with a few thin shims but I wonder if the crank is loose or maybe it was always like this.


I did check the cam as well and everything seemed good. Big difference is cam would stay at 0V all the time in the window. I tried the bypass as I monitored it to check for any engine reaction and there was none.

Does this model also use the cam to time the engine (ignition) or only CPS?

Like Noah said, welcome to the forum! I also love the testing and research you've done so far.

Just for my info, do I understand correctly that the previous shop replaced the ECM over the P0351 code? Since that's an ignition coil primary code, I'm figuring they had a spark problem.

I see that there's no coil control (again, love the notes)... I'd be interested to know what's happening on the white wire at the ignition module during cranking. This is the ECM's signal to the module for spark, and it should be some sort of 5V signal. These are known for broken wires at the coil connector (and sometimes inside the coil connector itself), so keep your eyes peeled Check out this thread by Rukerin:

scannerdanner.com/forum/post-your-repair...rm.html?limitstart=0

I understand that the P0315 is worrying, but I'd ignore it for now. You'll be able to complete the crank relearn procedure using a scanner later. That code won't cause a no start. Also, is that the only code you're getting? 'Cause I usually see P1626 Theft Deterrent Start Enable Signal Lost stored when there's an anti-theft concern.

Smart thinking by testing the crank sensor the way you did! I agree, the behavior is strange - the sensor should switch signals and stay switched the entire time it's near ferrous material. BUT, then how is there a reasonable RPM signal on the scanner?

Sorry I did forget to mention I did check my signal wire (white wire). I do have good continuity from module connector to ECM connector. I am not however, getting any signal. I guess it's the theft system keeping it from sparking. I did try to bypass with my test light connected to + and still not spark. Leads me to believe the module is bad, correct?

On the ECM side, it should be pin 26 on the green connector correct? It buzzes OK and no signs of short to ground.

So basically I might just be doing an incorrect relearn procedure.

From the crank I can see 217 to 235 rpm with my scanner as I crank.

I am not getting any other codes but P0315

Does this model rely on the cam sensor for position and/or firing? I think not because I try the bypass and no indication from anything clicking or turning on. Help is much appreciated.

New ECM just does not want to accept and I am also getting a P0351 in my pending DTC list.