Do I need a new PCM?
Thread Starter
Teching In
Joined: Feb 2009
Posts: 12
Likes: 0
From: Houston TX
Do I need a new PCM? I have a 5.3 swapped into a ‘71 C10 that has been driving great for over a year. I replaced a compressor that went out on my air ride system. Ever since then Bank 2 on my motor intermittently goes out, sometimes it’s right on startup, sometimes it happens after vehicle is warmed up, sometimes it goes out for a while then starts running fine again. It runs on only the 4 cylinders drivers side Bank 1 when the issue happens and it smells like fuel real bad until it fires back up. My Accuair system flashes red indicating low voltage.
Codes I’m getting are :
P0650
P1637
P1638
The things I’ve done to try and remedy the situation are:
Tuned with HP Tuners
replaced 02 sensors
Replaced the alternator with a high amp model
Replaced, cleaned and added grounds throughout the vehicle.
checked injectors, coils and plugs.
Checked voltage of the battery off and while running and it shows good.
With the vehicle throwing those codes I’m thinking either the wire to the alternator or the PCM itself is bad.
Can anyone help? I’m really struggling trying to fix this.
thanks
Codes I’m getting are :
P0650
P1637
P1638
The things I’ve done to try and remedy the situation are:
Tuned with HP Tuners
replaced 02 sensors
Replaced the alternator with a high amp model
Replaced, cleaned and added grounds throughout the vehicle.
checked injectors, coils and plugs.
Checked voltage of the battery off and while running and it shows good.
With the vehicle throwing those codes I’m thinking either the wire to the alternator or the PCM itself is bad.
Can anyone help? I’m really struggling trying to fix this.
thanks
There is a ground bundle that typically goes on the back of the drivers side head. This grounds the coils and injectors.
Check that it’s tight and that none of the wires in the ground lug have broken.
Check that it’s tight and that none of the wires in the ground lug have broken.
I would have a good look at the +12V circuit supplying the injectors and coils on that side as well,perhaps re think on how your alternator is wired into the system as well, I would wire it as a standalone not having anything to do with the PCM or it's wiring.
Thread Starter
Teching In
Joined: Feb 2009
Posts: 12
Likes: 0
From: Houston TX
This truck was running great for two years, one of which I had it. It’s just so weird that this is now happening.
Thread Starter
Teching In
Joined: Feb 2009
Posts: 12
Likes: 0
From: Houston TX
Ok so last night I found out that my Optima Red top was leaking gel acid.( it’s relocated behind the bumper in a custom bracket). I though it was just some small residue from me changing the coolant but with further inspection the battery is leaking.
I took it and had it replaced under warranty hoping this would resolve this issue and I’m still getting these codes.
next step is to diagnose either the PCM or the generator L wire at the alternator. My HP tuners is showing 0% for this wire while the vehicle is running. Anyone know how to properly test this wire?
car off I’m getting 12v and 14.2v while running so I don’t think it’s the alternator. Any ideas?
I took it and had it replaced under warranty hoping this would resolve this issue and I’m still getting these codes.
next step is to diagnose either the PCM or the generator L wire at the alternator. My HP tuners is showing 0% for this wire while the vehicle is running. Anyone know how to properly test this wire?
car off I’m getting 12v and 14.2v while running so I don’t think it’s the alternator. Any ideas?
Stock harness or aftermarket harness?
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TECH Fanatic
Joined: Dec 2017
Posts: 1,467
Likes: 265
From: Bossier City, Louisiana
I think you can ignore the P1637 or P1638 DTCs as long as the alternator is actually giving you a proper voltage at the battery with the engine running - let's say 14.2 volts DC at the battery posts. Check this at the battery with a good multimeter set to DC volts.Looks like you have already measured 14.2 at the battery. If it bothers you, turn those codes off in your tune.
I'm guessing your tune OS is newer than the model year of your harness.
Rick
I'm guessing your tune OS is newer than the model year of your harness.
Rick
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Verdad Gallardo You state the issue is intermittent. And when it's not running correctly, it's running on 4.
Common symptom of a bad ground.
From your manual:
6.3.3 Locate the three large ring terminals with BLACK and BLK/WHT wires and ground them to the engine. These must be on 3 separate bolts, DO NOT CONNECT ALL TO THE SAME GROUNDING POINT. Under no circumstance should all 3 ring terminals be connected to the same bolt.
Check these!
You also have separate fuses for Drivers side and Passenger side coils and injectors.
Check them.
When it's running bad, do you know which side isn't running? Find that side and measure the voltage at the coils and injectors.
Painless used the factory wiring colors. 12v is the PINK wire.
Check the grounds as well, with your volt meter. Those are either solid black or black with a colored stripe. There should not be 12v there.
Needs to be running poorly when you do this.
Ron
Common symptom of a bad ground.
From your manual:
6.3.3 Locate the three large ring terminals with BLACK and BLK/WHT wires and ground them to the engine. These must be on 3 separate bolts, DO NOT CONNECT ALL TO THE SAME GROUNDING POINT. Under no circumstance should all 3 ring terminals be connected to the same bolt.
Check these!
You also have separate fuses for Drivers side and Passenger side coils and injectors.
Check them.
When it's running bad, do you know which side isn't running? Find that side and measure the voltage at the coils and injectors.
Painless used the factory wiring colors. 12v is the PINK wire.
Check the grounds as well, with your volt meter. Those are either solid black or black with a colored stripe. There should not be 12v there.
Needs to be running poorly when you do this.
Ron