P1637 Bad PCM?
Thread Starter
Intermediate
Joined: Jul 2018
Posts: 44
Likes: 6
P1637 Bad PCM?
2003 Z06
I have the code P1637 (Generator L-Terminal Circuit) and I'm looking for some help resolving it hoping it's not my PCM. I got this car on the cheap and have been fixing all the problems with it. This is my very last code and it will be a huge relief when it is gone.
My voltage was a tad low at 13.5-8 (running) so this is what I have done so far...
- Replaced regulator in the alternator - now reads ~14.5 running - this is the one I purchased https://www.ebay.com/itm/221824904744
- Replaced the battery (had a brand new one in a 4th gen parts car I bought - not just throwing money at it)
- Checked all the grounds
- Checked all the connections on the starter solenoid
- Verified the alternator is the correct 145 amp - Note: it is NOT a Valeo alternator and I know that could potentially be an issue. However I want to be 1000% sure before I drop that kinda money.
I still am getting the code, charge system fault, and service engine soon on my DIC. The voltage has no notable drop with accessories on even for extended periods. (headlights, radio, etc). The voltage is being checked with a multimeter, not just running off the gauge.
Specs on the car if they matter:
Ported 243 heads
Ported LS2 Intake
Comp Cam
Forged Internals
Longtubes
I have the code P1637 (Generator L-Terminal Circuit) and I'm looking for some help resolving it hoping it's not my PCM. I got this car on the cheap and have been fixing all the problems with it. This is my very last code and it will be a huge relief when it is gone.
My voltage was a tad low at 13.5-8 (running) so this is what I have done so far...
- Replaced regulator in the alternator - now reads ~14.5 running - this is the one I purchased https://www.ebay.com/itm/221824904744
- Replaced the battery (had a brand new one in a 4th gen parts car I bought - not just throwing money at it)
- Checked all the grounds
- Checked all the connections on the starter solenoid
- Verified the alternator is the correct 145 amp - Note: it is NOT a Valeo alternator and I know that could potentially be an issue. However I want to be 1000% sure before I drop that kinda money.
I still am getting the code, charge system fault, and service engine soon on my DIC. The voltage has no notable drop with accessories on even for extended periods. (headlights, radio, etc). The voltage is being checked with a multimeter, not just running off the gauge.
Specs on the car if they matter:
Ported 243 heads
Ported LS2 Intake
Comp Cam
Forged Internals
Longtubes
Last edited by FoxZ06; Aug 23, 2018 at 07:45 PM.
Race Director
Joined: Apr 2007
Posts: 11,152
Likes: 890
From: South Western Ontario
What are the voltages on the L terminal with engine off key on and with engine running?
Does it begin to charge within a second or two when it is started?
If you use the correct regulator then you don't need the rest of the alternator to say Valeo on it.
Does it begin to charge within a second or two when it is started?
If you use the correct regulator then you don't need the rest of the alternator to say Valeo on it.
Race Director
Joined: Apr 2007
Posts: 11,152
Likes: 890
From: South Western Ontario
L wire is the smaller red wire in the connector on terminal B. Yes, meter on the red wire and ground - alternator case will work. Do it with the connector plugged in so you have to back probe the wire.
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Race Director
Joined: Apr 2007
Posts: 11,152
Likes: 890
From: South Western Ontario
That's what I would expect with it unplugged. I would tend to suspect the regulator is bad. Apparently, depending on the year of car it could have used 1 of 2 different regulators. I think the M520 is correct, and the other was maybe a M521.
Thread Starter
Intermediate
Joined: Jul 2018
Posts: 44
Likes: 6
I just installed the new M520, and while it brought my voltage up a bit it didn't get the message to go away. I've reset it a couple of times with no luck.
I got the M520 based off of this thread
https://www.corvetteforum.com/forums...nd-issues.html
I got the M520 based off of this thread
https://www.corvetteforum.com/forums...nd-issues.html