96 chevy k2500 random no start
November 11th, 2022, 3:36 PM
#21
CF Beginner
Thread Starter
I'll check the wiring again and look closer about a wire possibly jossled loose. I feel that if the wire was loose it would shut the truck off during driving over bumps and such. The key feels pretty secure and doesnt really show signs of wear such as being able to pull the key out with truck on still. I'll look into the ignition switch next
November 11th, 2022, 3:58 PM
#22
CF Monarch
I'll check the wiring again and look closer about a wire possibly jossled loose. I feel that if the wire was loose it would shut the truck off during driving over bumps and such. The key feels pretty secure and doesnt really show signs of wear such as being able to pull the key out with truck on still. I'll look into the ignition switch next
November 16th, 2022, 7:19 PM
#23
CF Beginner
Thread Starter
ok so update on the random no start issues, the truck has been sitting for about 5 days. each day i check and see if it will start but nothing, I've been working so havent been able to diagnose till today. Today i went out and went through some diagnosis, I was getting good fuel pressure (60psi) and to check spark I just shot start fluid in the intake and no start not even a cough. I know I was testing for the crank sensor back when i had no start issues in california but I always had a tack signal then so i grabbed my scanner and checked for a tack signal during cranking and sure enough zero signal. Swapped out the sensor and the truck fired right up. Unfortunetly I dont believe this is my issue because when I was having no start issues in california I put in a new crank sensor and it still didnt start the truck then. So basically I added an issue during the 400 mile drive so that is now fixed but im still waiting for the day the truck randomly will not start again seeing as I have yet to fix the random no start issue. If i have any no start issues again then i will come back and update the forum. thank you to all for the ideas and assistance in diagnosing.
December 19th, 2022, 2:16 PM
#24
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I have a 2011 1500, however, your symptoms sound very similar to mine. Everything would work perfect for days or weeks then no-start for a day or two. It was very frustrating and ended up being a couple of issues that originally started from bad battery cables, however, that wasn’t the only solution.
To start with, the positive and negative battery cables were corroded inside the cable and prevented sufficient voltage and amperage getting to all necessary components and computer modules during starting. I replaced those initially and cleaned the ground locations when I did. The no-start situations were less frequent, but still happened. I threw a new starter and new generator at it and still had random no-starts. those two parts didn’t improve anything.
Fuel supply was fine when it would work, but non-existent when it was in a no-start situation.
The next step in the solution was to change the high-amp 175 amp mega fuse. On my truck it was right where the generator cable connnectd to the battery. I know others are mounted elsewhere like the firewall. The fuse wasn’t blown, but the contacts were corroded, I’m sure interior of fuse was corroded as well (never looked, it was $4.99 so I didn’t care).
That significantly improved the frequency of my no-starts, however, when they did occur they were now accompanied with a ‘service anti-theft module’ message.
Your year model may have a different system, but apparently, age, vibration and electrical power surges/drops from the bad cables has damaged the module that reads the programmed key.
That mis-read of the anti-theft key was telling the pcm to prevent starts, which includes not sending power to the fuel pump.
Fixing that module was the final remedy. if your key has a black plastic end where you hold it to turn, it is passkey 3. The module was really easy to change, about 5 min, BUT it has to be reprogrammed to work.
Tip if you change the theft module…if it is the passkey 3 system you *can* program it yourself using a 30 minute re-learn procedure. However, the pcm requires a constant 12 volts. If it senses a voltage drop or surge outside of 12 volts it kicks you out of the re-learn procedure. If you have a battery tender it needs to be a steady voltage/old style one. A newer, digital varying voltage charger/tender will change the voltage too much and you’ll get kicked out of the re-learn procedure before it can complete.
Learned that after a very frustrating 2 hours. I ended up just getting a friend to trailer it to the dealership and they programmed it in about an hour for one hour shop time.
To start with, the positive and negative battery cables were corroded inside the cable and prevented sufficient voltage and amperage getting to all necessary components and computer modules during starting. I replaced those initially and cleaned the ground locations when I did. The no-start situations were less frequent, but still happened. I threw a new starter and new generator at it and still had random no-starts. those two parts didn’t improve anything.
Fuel supply was fine when it would work, but non-existent when it was in a no-start situation.
The next step in the solution was to change the high-amp 175 amp mega fuse. On my truck it was right where the generator cable connnectd to the battery. I know others are mounted elsewhere like the firewall. The fuse wasn’t blown, but the contacts were corroded, I’m sure interior of fuse was corroded as well (never looked, it was $4.99 so I didn’t care).
That significantly improved the frequency of my no-starts, however, when they did occur they were now accompanied with a ‘service anti-theft module’ message.
Your year model may have a different system, but apparently, age, vibration and electrical power surges/drops from the bad cables has damaged the module that reads the programmed key.
That mis-read of the anti-theft key was telling the pcm to prevent starts, which includes not sending power to the fuel pump.
Fixing that module was the final remedy. if your key has a black plastic end where you hold it to turn, it is passkey 3. The module was really easy to change, about 5 min, BUT it has to be reprogrammed to work.
Tip if you change the theft module…if it is the passkey 3 system you *can* program it yourself using a 30 minute re-learn procedure. However, the pcm requires a constant 12 volts. If it senses a voltage drop or surge outside of 12 volts it kicks you out of the re-learn procedure. If you have a battery tender it needs to be a steady voltage/old style one. A newer, digital varying voltage charger/tender will change the voltage too much and you’ll get kicked out of the re-learn procedure before it can complete.
Learned that after a very frustrating 2 hours. I ended up just getting a friend to trailer it to the dealership and they programmed it in about an hour for one hour shop time.
December 19th, 2022, 2:36 PM
#25
CF Beginner
Thread Starter
I have a 2011 1500, however, your symptoms sound very similar to mine. Everything would work perfect for days or weeks then no-start for a day or two. It was very frustrating and ended up being a couple of issues that originally started from bad battery cables, however, that wasn’t the only solution.
To start with, the positive and negative battery cables were corroded inside the cable and prevented sufficient voltage and amperage getting to all necessary components and computer modules during starting. I replaced those initially and cleaned the ground locations when I did. The no-start situations were less frequent, but still happened. I threw a new starter and new generator at it and still had random no-starts. those two parts didn’t improve anything.
Fuel supply was fine when it would work, but non-existent when it was in a no-start situation.
The next step in the solution was to change the high-amp 175 amp mega fuse. On my truck it was right where the generator cable connnectd to the battery. I know others are mounted elsewhere like the firewall. The fuse wasn’t blown, but the contacts were corroded, I’m sure interior of fuse was corroded as well (never looked, it was $4.99 so I didn’t care).
That significantly improved the frequency of my no-starts, however, when they did occur they were now accompanied with a ‘service anti-theft module’ message.
Your year model may have a different system, but apparently, age, vibration and electrical power surges/drops from the bad cables has damaged the module that reads the programmed key.
That mis-read of the anti-theft key was telling the pcm to prevent starts, which includes not sending power to the fuel pump.
Fixing that module was the final remedy. if your key has a black plastic end where you hold it to turn, it is passkey 3. The module was really easy to change, about 5 min, BUT it has to be reprogrammed to work.
Tip if you change the theft module…if it is the passkey 3 system you *can* program it yourself using a 30 minute re-learn procedure. However, the pcm requires a constant 12 volts. If it senses a voltage drop or surge outside of 12 volts it kicks you out of the re-learn procedure. If you have a battery tender it needs to be a steady voltage/old style one. A newer, digital varying voltage charger/tender will change the voltage too much and you’ll get kicked out of the re-learn procedure before it can complete.
Learned that after a very frustrating 2 hours. I ended up just getting a friend to trailer it to the dealership and they programmed it in about an hour for one hour shop time.
To start with, the positive and negative battery cables were corroded inside the cable and prevented sufficient voltage and amperage getting to all necessary components and computer modules during starting. I replaced those initially and cleaned the ground locations when I did. The no-start situations were less frequent, but still happened. I threw a new starter and new generator at it and still had random no-starts. those two parts didn’t improve anything.
Fuel supply was fine when it would work, but non-existent when it was in a no-start situation.
The next step in the solution was to change the high-amp 175 amp mega fuse. On my truck it was right where the generator cable connnectd to the battery. I know others are mounted elsewhere like the firewall. The fuse wasn’t blown, but the contacts were corroded, I’m sure interior of fuse was corroded as well (never looked, it was $4.99 so I didn’t care).
That significantly improved the frequency of my no-starts, however, when they did occur they were now accompanied with a ‘service anti-theft module’ message.
Your year model may have a different system, but apparently, age, vibration and electrical power surges/drops from the bad cables has damaged the module that reads the programmed key.
That mis-read of the anti-theft key was telling the pcm to prevent starts, which includes not sending power to the fuel pump.
Fixing that module was the final remedy. if your key has a black plastic end where you hold it to turn, it is passkey 3. The module was really easy to change, about 5 min, BUT it has to be reprogrammed to work.
Tip if you change the theft module…if it is the passkey 3 system you *can* program it yourself using a 30 minute re-learn procedure. However, the pcm requires a constant 12 volts. If it senses a voltage drop or surge outside of 12 volts it kicks you out of the re-learn procedure. If you have a battery tender it needs to be a steady voltage/old style one. A newer, digital varying voltage charger/tender will change the voltage too much and you’ll get kicked out of the re-learn procedure before it can complete.
Learned that after a very frustrating 2 hours. I ended up just getting a friend to trailer it to the dealership and they programmed it in about an hour for one hour shop time.
December 19th, 2022, 3:18 PM
#26
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One more note, I also pulled codes during that time for high and low voltage crank position sensors that didn’t make any sense. I didn’t have any drive ability issues once it did start. I did have a code for a bank 2 sensor 2 O2 sensor which I replaced. Probably not related, but with electrical you never know. Good Luck I know the frustration!
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