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I just dusted off my car after sitting for about a year. I would on occasion start it and let it run. When not driven, battery charge is maintained using a battery tender. A P1637 L code appeared inside dash. Replaced the battery with AC Delco Replacement and reset the the code. After starting, the same code reappeared. Service Engine Soon flashed across the dash. The car has 3200 miles. Never had an issue with it. All fluids changed and maintained. What should I look for?
I just dusted off my car after sitting for about a year. I would on occasion start it and let it run. When not driven, battery charge is maintained using a battery tender. A P1637 L code appeared inside dash. Replaced the battery with AC Delco Replacement and reset the the code. After starting, the same code reappeared. Service Engine Soon flashed across the dash. The car has 3200 miles. Never had an issue with it. All fluids changed and maintained. What should I look for?
P1637 code is for the Generator turn-on circuit. The PCM sends a 5-volt signal to the generator's voltage regulator. If it does not see the correct voltage at the generators L-term connection it sets this code. Need to check Pin B (red) wire for 5 volts. The generators voltage regulator can have a problem and ground the circuit and cause a low voltage there and cause the code to set, or there is a problem from the PCM to the generators L-Term connection to send the 5 volts to turn on the generator.
So either a voltage issue from the PCM to the generator L-Term connector or a bad voltage regulator in the generator are the 2 likely causes. Actually, I would expect a charge system fault error with this code.
Last edited by RedRiderZR1; May 10, 2018 at 10:43 PM.
P1637 code is for the Generator turn-on circuit. The PCM sends a 5-volt signal to the generator's voltage regulator. If it does not see the correct voltage at the generators L-term connection it sets this code. Need to check Pin B (red) wire for 5 volts. The generators voltage regulator can have a problem and ground the circuit and cause a low voltage there and cause the code to set, or there is a problem from the PCM to the generators L-Term connection to send the 5 volts to turn on the generator.
So either a voltage issue from the PCM to the generator L-Term connector or a bad voltage regulator in the generator are the 2 likely causes. Actually, I would expect a charge system fault error with this code.
Yes. The "Charge System Fault" did appear. I thought by resetting (ie. clearing code on DIC) that it that it would go away once I installed the new battery. The car is stored in climate controlled shop so perhaps moisture would not be an issue. Unplugging the harness from the alternator and checking red wire for 5 volts with the ignition turned on?
Last edited by Burgundyman93; May 10, 2018 at 11:06 PM.
Yes. The "Charge System Fault" did appear. I thought by resetting (ie. clearing code on DIC) that it that it would go away once I installed the new battery. The car is stored in climate controlled shop so perhaps moisture would not be an issue. Unplugging the harness from the alternator and checking red wire for 5 volts with the ignition turned on?
yes, engine on, should see 5 volts at PIN B (red) wire. If not, there is a open in that wire or PCM not sending 5 volts. If you do see 5 volts with connector off of alternator than quite possibly bad voltage regulator in the alternator. That can be tested by plugging in the connector to the alternator and if the voltage on that pin drops the protection circuit in the alternator is grounding that circuit and causing the code. Then you have a bad voltage regulator in the alternator.
edit: I checked the service manual and it said to check the voltage with the connector disconnected with the ENGINE ON.
Here is the pinout on the connector
Last edited by RedRiderZR1; May 10, 2018 at 11:34 PM.
yes, engine on, should see 5 volts at PIN B (red) wire. If not, there is a open in that wire or PCM not sending 5 volts. If you do see 5 volts with connector off of alternator than quite possibly bad voltage regulator in the alternator. That can be tested by plugging in the connector to the alternator and if the voltage on that pin drops the protection circuit in the alternator is grounding that circuit and causing the code. Then you have a bad voltage regulator in the alternator.
edit: I checked the service manual and it said to check the voltage with the connector disconnected with the ENGINE ON.
Here is the pinout on the connector
The only code is 1637 H...the battery reads 12.67 when engine is off. It reads 13.67 when engine is idling. The voltage at the alternator is slightly higher about 13.75 while idling. Pin B is about 10 volts? not 5.
So I took the car for a lengthy drive. The alternator was showing less that 13 volts on the dash gauge. Maybe about 12.5 volts. Two codes appeared on DIC: 10-PCM P1367 H and 60-IPC B1543 H. These are the only two codes. The Service Engine Soon message is still displayed. While the engine was running I check the voltage at the alternator. It was about 12.5 as compared to 13.67 a couple of days ago. Ironically, I did see a charging system warning message when I started car before taking it for a ride. I changed the oil a few days ago. Does this have anything to do with 60-IPC B1543 H? I hope my alternator does not need replacement. Any help at this point is welcomed. Maybe PCM?
Last edited by Burgundyman93; May 13, 2018 at 09:18 PM.
So I took the car for a lengthy drive. The alternator was showing less that 13 volts on the dash gauge. Maybe about 12.5 volts. Two codes appeared on DIC: 10-PCM P1367 H and 60-IPC B1543 H. These are the only two codes. The Service Engine Soon message is still displayed. While the engine was running I check the voltage at the alternator. It was about 12.5 as compared to 13.67 a couple of days ago. Ironically, I did see a charging system warning message when I started car before taking it for a ride. I changed the oil a few days ago. Does this have anything to do with 60-IPC B1543 H? I hope my alternator does not need replacement. Any help at this point is welcomed. Maybe PCM?
UPDATE: Replaced Alternator with a GM REMAN ($225.00) and two years warantee. I did could not see buying a new one for $365 and one year warantee. Problem fixed
The only code is 1637 H...the battery reads 12.67 when engine is off. It reads 13.67 when engine is idling. The voltage at the alternator is slightly higher about 13.75 while idling. Pin B is about 10 volts? not 5.
Piggybacking on this post. I've recently started experiencing a 1637 code. I'm getting 10.xx volts on Pin B (tested both between the plug and the alternator terminal and the plug and ground... same voltage). Does this mean my alternator is bad?
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P1637 L code 2003
