Crank No Start only on first try

Sergio Technician Texas Posted   Latest   Edited  
Updated
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2003 Chevrolet Silverado 1500 4.8L (V) 4-spd (4L60-E) — 1GCEK14V63Z358389
Crank / No Start

Condition: This vehicle will crank but will not start but only occurs on the first ignition cycle. The concern usually occurs 6-8 hours after the vehicle has been sitting but can be duplicated again if the battery is disconnected and the touching the terminals together for about 10min. 

Background: The vehicle originally came to our shop with a no crank no start concern as well as this current problem. The customer also had us replace the engine so the engine and transmission were removed during this visit-the starting conditions were occurring before and after the engine replacement, The starting concerns were not looked into until after the engine was replaced. The no start no crank was found to be a faulty wiring repair by the customer (loose, taped up wiring) done to the run/crank circuit under the fuse box and has not occurred since the wiring was repaired. When the crank no start issue happens the ignition coils are sparking and fuel pressure is present (56-58psi) within a second of cranking. The fuel injectors are not being given an ‘on’ command when viewed with a scope during the event which leads me to believe the VTD (vehicle theft deterrent) system is disabling an engine start. A fault code [BCM: B2961] was found, the switch detecting the key position was found to be worn out and not detecting the key in the crank/run position and was believed to be causing the issue but replacing that switch did not correct the concern. Replacing the key position switch did, however, fix the B2961 fault-No fault codes have appeared since that was replaced even after multiple crank no start events. The security light turns off during the crank no start. The cam and crank sensors have been replaced and the cam/crank variation relearn has already been performed. The passlock sensor w/ignition housing has also been replaced and did not change the condition. The range selector switch has been replaced, this did not change the condition. The range selector switch position can be read from the instrument cluster live data. The ‘PRNDL’ indicator does not show in the center display of the cluster, the customer informed us that the cluster was from another truck and that function has not worked since the cluster replacement, they were not able to remember how long ago the cluster was replaced. There were aftermarket accessories (a bullydog tuner, aftermarket radio, A pillar tweeters) on the vehicle, removing these and putting the wiring back to how it was did not change the condition. 

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Jesse Owner/Technician
Georgia
Jesse
 

Use scan tool to see if pcm is resetting first thing after sitting, seems like disconnecting the battery is resetting the pcm and causing the no start concern. Then it learns the parameters and starts fine every time till it resets again.. See if the p1000 code is set before starting or check in data pid for ecm reset count. If it is then power and ground check to pcm and possible replacement…

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Agree
Sergio Technician
Texas
Sergio
 

There are no fault codes in any module except a dimmer switch fault in the BCM (unrelated), I've disconnected the PCM and will check in about 30min to see if the condition re-occurs

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Sergio Technician
Texas
Sergio
   

After disconnecting the PCM for approx 30 min the condition re-occurs. I disconnected the PCM for 15min and the condition re-occurs again. I will be checking the serial data line for proper communication from the BCM and looking at the rest of the wiring diagram to see if the PCM has anything that keeps the internal memory constantly powered. I'm unsure what this test indicates and will have to…

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Jesse Engineer
Missouri
Jesse
   

The basic overview sounds like typical weak fuel pump/fuel pressure regulator. Overnight, the fuel pressure bleeds down, bad fuel pressure regulator. I believe these are on the fuel rail. Pull the vacuum hose and see if any gas runs out of it. If so, the regulator is bad. To test for weak pump, let sit for awhile, turn key on for 3-5 seconds to prime fuel system, turn off, turn back on for 3-5…

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Disagree
Sergio Technician
Texas
Sergio
 

I have already “pre-primed” the fuel pump before cranking by manually actuating the fuel pump relay and the issue still re-occurs. The fuel pump was replaced earlier during the visit as well. I have not bypassed the VTD system because the passlock sensor was replaced-I will look into the bypass steps but it seems to be the equivalent of a replacement passlock sensor by changing the resistance…

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James Technician
California
James
 

I read a lot of the history-WOW! Did not read it all though. I believe I know what it is. I had the same issue last year on a Chevy. It was caused by a cheap aftermarket cam sensor that we installed. A good OEM one solved my problem. I found it by scoping the cam and crank signals when starting. The cam sensor had a slight delay before it would start working, maybe a few milliseconds, but enough…

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Sergio Technician
Texas
Sergio
 

Unfortunately the cam sensor has been replaced a few times this visit. The first time it was replaced (Autopart International part) the signal was faulty, and it was replaced again later (Carquest premium part) in the diagnosis because we thought it may have been faulty again. The sensor signal seemed to be immediate but we did not use an AC Delco part. We have talked with the customer and they…

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James Technician
California
James
 

If you do get it back, set your scope trigger to capture only when there is a signal, and trigger it off of the crank signal. Auto trigger will not capture it.

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Sergio Technician
Texas
Sergio Update
 

The customer has decided they do not want to continue further diagnosis of the concern. A full summary of all the steps taken to address the issue is in the PDF attached. Thank you all for the support!

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Update Ð Awarded
Randall Owner/Technician
Michigan
Randall
 

I truly hope that many will read the summary of this repair. Holy s*** would be an understatement. My message to my techs at our next weekly meeting is as follows: “why we can't assume where any diag is headed” along with a review of your summary. I hope you got paid well enough Thank You for posting and all your personal time and organization into the summary.

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Sergio Technician
Texas
Sergio
 

I only wish I could've fixed the issue, I've only seen 2 or 3 other cases of this concern happening on forums and 1 with IdentiFix but with no confirmed resolution of the problem. We can never truly guarantee that we will find the answer but I tried as hard as I could. It definitely had an impact on how I will approach potential “problem vehicles” in the future. Thorough documentation and proper…

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