PCM Constant Power Issue
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Teching In
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PCM Constant Power Issue Hey everyone,
sorry if I’m posting this in the wrong place. I have a 5.3 in an 04 Escalade. I’m having a problem where when the key is turned off, the PCM resets itself. Like it’s losing all of its memory. I noticed this when I couldn’t pass emissions on account of my I/M monitors would be ready when driving on the way to the station. But when they made me turn the car off then back on, the monitors would be incomplete.
What do I need to start checking?
Thanks!!!
sorry if I’m posting this in the wrong place. I have a 5.3 in an 04 Escalade. I’m having a problem where when the key is turned off, the PCM resets itself. Like it’s losing all of its memory. I noticed this when I couldn’t pass emissions on account of my I/M monitors would be ready when driving on the way to the station. But when they made me turn the car off then back on, the monitors would be incomplete.
What do I need to start checking?
Thanks!!!
TECH Fanatic
Joined: Dec 2017
Posts: 1,467
Likes: 265
From: Bossier City, Louisiana
What colors are your PCM connectors? This will tell us whether you have a P01 PCM or a P59. I suspect yours will be a blue and a green connector P59. You should also be seeing some slight difficulty starting and a poor idle here until your PCM relearns how to behave.
Then go here:
https://lt1swap.com/2004vortec_pcm.htm
Looks like a bad Blue Pin 20 or Pin 57 connector wire somewhere for you. Should be an orange wire for both of these on that connector loom.
I see nothing on the Green connector that I'd be very concerned about except also maybe the black wire grounds to the PCM for both blue and green connectors.
Rick
Then go here:
https://lt1swap.com/2004vortec_pcm.htm
Looks like a bad Blue Pin 20 or Pin 57 connector wire somewhere for you. Should be an orange wire for both of these on that connector loom.
I see nothing on the Green connector that I'd be very concerned about except also maybe the black wire grounds to the PCM for both blue and green connectors.
Rick
Thread Starter
Teching In
Joined: Jul 2021
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What colors are your PCM connectors? This will tell us whether you have a P01 PCM or a P59. I suspect yours will be a blue and a green connector P59. You should also be seeing some slight difficulty starting and a poor idle here until your PCM relearns how to behave.
Then go here:
https://lt1swap.com/2004vortec_pcm.htm
Looks like a bad Blue Pin 20 or Pin 57 connector wire somewhere for you. Should be an orange wire for both of these on that connector loom.
I see nothing on the Green connector that I'd be very concerned about except also maybe the black wire grounds to the PCM for both blue and green connectors.
Rick
Then go here:
https://lt1swap.com/2004vortec_pcm.htm
Looks like a bad Blue Pin 20 or Pin 57 connector wire somewhere for you. Should be an orange wire for both of these on that connector loom.
I see nothing on the Green connector that I'd be very concerned about except also maybe the black wire grounds to the PCM for both blue and green connectors.
Rick
I disconnected the battery & pulled the PCM out. If I plug the battery back in and put a multimeter probe into Pin 19, should I be seeing 12 volts? Or does the harness need to be fixed plugged in to the PCM to see the constant power?
The connectors going into the PCM do have 2 wires from the E-Fan setup getting spliced in, but I don’t think that’s causing any issues.
Where do I go from here?
TECH Fanatic
Joined: Dec 2017
Posts: 1,467
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From: Bossier City, Louisiana
Pin 19 has nothing to do with your problem - Pin 19 is PCM ignition "boot up" power, not memory retention. As mentioned above, your most likely concern is at PIN 20 or Pin 57. Or possible one of the PCM grounds.
With the ignition key on, you should see power on pin 19. Turn the key off, no power on pin 19. For pin 20 and pin 57, they should have power all the time to retain learned memory parameters.
Please tell me more about your E-fan setup. I hope you are controlling the fans through a relay because the PCM is unable to do it directly.
Rick
With the ignition key on, you should see power on pin 19. Turn the key off, no power on pin 19. For pin 20 and pin 57, they should have power all the time to retain learned memory parameters.
Please tell me more about your E-fan setup. I hope you are controlling the fans through a relay because the PCM is unable to do it directly.
Rick
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From: Central Cal.
The PCM just has the 2 ground connections needed. Look up ls1fans for a 3-relay harness that will connect easily and run the fans almost like the factory set up. Or buy a PWM controller for smoother operation.
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Teching In
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*disclaimer* the previous owner did the e-fans, so I only know what he told me and what I can see. The fans are wired into two relays. The relays each have a wire running to the PCM, that is T’d into the harness just before the pins.
P.O. told me he had software and setup the 1st fan to come on at 185 @ the 2nd at 190.
I’m going to test the power at the connectors today to see if I’m getting 12v with the key off at the 2 constant power pins.
P.O. told me he had software and setup the 1st fan to come on at 185 @ the 2nd at 190.
I’m going to test the power at the connectors today to see if I’m getting 12v with the key off at the 2 constant power pins.
Thread Starter
Teching In
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☹️ Not what I wanted to hear. Do I need to buy HP Tuners so my fans work? Is there a cheaper way I can get my new PCM tuned for E-Fans?
TECH Fanatic
Joined: Dec 2017
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From: Bossier City, Louisiana
I can do blue / green P59 PCM devices here for free using Tuner Pro RT / PCM Hammer / LS Droid - no HP Tuners credits required. Lots of You Tube videos about these capabilities if you are interested. Things might be a little harder to do with these three but overall, not bad. Buy or build your own bench harness is almost mandatory here.
Rick
Rick
Thread Starter
Teching In
Joined: Jul 2021
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I can do blue / green P59 PCM devices here for free using Tuner Pro RT / PCM Hammer / LS Droid - no HP Tuners credits required. Lots of You Tube videos about these capabilities if you are interested. Things might be a little harder to do with these three but overall, not bad. Buy or build your own bench harness is almost mandatory here.
Rick
Rick
built a bench harness. Bought a junkyard pcm. Read entire Escalade PCM that was in truck. Flashed clone to junkyard PCM. Put junkyard PCM in the truck. Same issue, it’s losing parameters when the key is off.
What am I missing here? Was cloning the original PCM a mistake?
TECH Fanatic
Joined: Dec 2017
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From: Bossier City, Louisiana
Perhaps. If there was a software error in your original tune, you just copied it to the new PCM. But you have not harmed the new PCM, we just need to put a good operating system into it.
Are you getting power on pin 20 and pin 57 on the PCM side of the long connector blocks or the engine side of the long connector blocks? Where did you measure at pin 20 and pin 57? Ideally, it would be a measurement on the PCM side of the long connector to somewhat eliminate a "pushed" female side of these connectors.
Rick
Are you getting power on pin 20 and pin 57 on the PCM side of the long connector blocks or the engine side of the long connector blocks? Where did you measure at pin 20 and pin 57? Ideally, it would be a measurement on the PCM side of the long connector to somewhat eliminate a "pushed" female side of these connectors.
Rick
Thread Starter
Teching In
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Perhaps. If there was a software error in your original tune, you just copied it to the new PCM. But you have not harmed the new PCM, we just need to put a good operating system into it.
Are you getting power on pin 20 and pin 57 on the PCM side of the long connector blocks or the engine side of the long connector blocks? Where did you measure at pin 20 and pin 57? Ideally, it would be a measurement on the PCM side of the long connector to somewhat eliminate a "pushed" female side of these connectors.
Rick
Are you getting power on pin 20 and pin 57 on the PCM side of the long connector blocks or the engine side of the long connector blocks? Where did you measure at pin 20 and pin 57? Ideally, it would be a measurement on the PCM side of the long connector to somewhat eliminate a "pushed" female side of these connectors.
Rick
Is there a way I could go into Tuner Pro and have Readiness Indicators always read “OK”?
TECH Fanatic
Joined: Dec 2017
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From: Bossier City, Louisiana
I see that its a 5.3 liter engine but what transmission do you have? 4L60E? I likely have a tune I could send you to put into your new junk yard PCM but for now, leave your original PCM alone. Always, always leave yourself a good PCM to run the vehicle with - ALWAYS!!! Is this your daily driver vehicle?
What state are you in and does it have strict emissions control laws?
Rick
What state are you in and does it have strict emissions control laws?
Rick