GMC Truck Forum banner
1 - 17 of 17 Posts

·
Registered
Joined
·
226 Posts
Discussion Starter · #1 ·
Went to lunch today and on the way back my battery light was on and I got that messade on my display. What does that mean and how do I fix it?
 

·
Resident Guinea ***
Joined
·
14,535 Posts
You probably have a code as well.

(generator = alternator)

P1637

CIRCUIT DESCRIPTION
The powertrain control module (PCM) uses the generator turn on signal circuit to control the generator. A high side driver within the PCM allows the PCM to turn the generator ON and OFF. When Generator operation is desired, the PCM sends a 5 volt signal to the voltage regulator via the generator turn on signal circuit. This causes the voltage regulator to begin controlling the generator field circuit. Once the Generator is enabled by the PCM, the voltage regulator controls generator output independently of the PCM. Under certain operating conditions, the PCM can turn Off the generator by turning Off the 5 volt signal on the generator turn on signal circuit. The PCM has fault detection circuitry which monitors the state of the generator turn on signal circuit. If the fault detection circuit senses a voltage other than what is expected, this DTC will set. The voltage regulator also contains fault detection circuitry. If the regulator detects a problem, the regulator will ground the generator turn on signal circuit, pulling the voltage low. This also causes the PCM to set the DTC.

CONDITIONS FOR RUNNING THE DTC


The ignition is on.
System voltage between 9.0 and 18.0 volts .
CONDITIONS FOR SETTING THE DTC


An improper voltage level has been detected on the generator L-terminal circuit.
The above conditions are present for at least 30 seconds .
ACTION TAKEN WHEN THE DTC SETS
The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

CONDITIONS FOR CLEARING THE MIL/DTC


The DTC becomes history when the conditions for setting the DTC are no longer present.
The history DTC clears after 40 malfunction free warm-up cycles.
The PCM receives a clear code command from the scan tool.
 

·
Registered
Joined
·
226 Posts
Discussion Starter · #4 ·
You probably have a code as well.

(generator = alternator)

P1637

CIRCUIT DESCRIPTION
The powertrain control module (PCM) uses the generator turn on signal circuit to control the generator. A high side driver within the PCM allows the PCM to turn the generator ON and OFF. When Generator operation is desired, the PCM sends a 5 volt signal to the voltage regulator via the generator turn on signal circuit. This causes the voltage regulator to begin controlling the generator field circuit. Once the Generator is enabled by the PCM, the voltage regulator controls generator output independently of the PCM. Under certain operating conditions, the PCM can turn Off the generator by turning Off the 5 volt signal on the generator turn on signal circuit. The PCM has fault detection circuitry which monitors the state of the generator turn on signal circuit. If the fault detection circuit senses a voltage other than what is expected, this DTC will set. The voltage regulator also contains fault detection circuitry. If the regulator detects a problem, the regulator will ground the generator turn on signal circuit, pulling the voltage low. This also causes the PCM to set the DTC.

CONDITIONS FOR RUNNING THE DTC


The ignition is on.
System voltage between 9.0 and 18.0 volts .
CONDITIONS FOR SETTING THE DTC


An improper voltage level has been detected on the generator L-terminal circuit.
The above conditions are present for at least 30 seconds .
ACTION TAKEN WHEN THE DTC SETS
The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

CONDITIONS FOR CLEARING THE MIL/DTC


The DTC becomes history when the conditions for setting the DTC are no longer present.
The history DTC clears after 40 malfunction free warm-up cycles.
The PCM receives a clear code command from the scan tool.
So new alternator?
 

·
Registered
Joined
·
157 Posts
Is the alternator dirty? I got that message once, opened the hood and the alternator was caked in mud. I cleaned it all off and it has been fine ever since.
 

·
Registered
Joined
·
6,155 Posts
my alt. is a year old and it has started doin that shit to me again, except this time its only at lower rpm while driving or idle.
 

·
Registered
Joined
·
2 Posts
So same thi happened to me, I cleaned up the negative battery terminal, unplugged everything from the interior power outlets, touched what I think is the R-Terminal with a screwdriver (someone told me to try it) and idled the truck for 20 and it was fine. Next day I'm driving home and the warning came on again, tried the same stuff and nothing this time... Any suggestions?
 

·
Registered
Joined
·
39 Posts
Resurrecting an old thread....

I replaced the intake manifold gaskets yesterday, then got this error when starting the truck this morning.

I'm guessing I didn't connect the alternator up properly, or I broke a wire loose when moving all the interference around.

I'm open to any other suggestions as to what to look for when I get home today. It was 25 degrees out this morning, so I wasn't gonna mess around with troubleshooting...
 

·
Registered
Joined
·
39 Posts
Resurrecting an old thread....

I replaced the intake manifold gaskets yesterday, then got this error when starting the truck this morning.

I'm guessing I didn't connect the alternator up properly, or I broke a wire loose when moving all the interference around.

I'm open to any other suggestions as to what to look for when I get home today. It was 25 degrees out this morning, so I wasn't gonna mess around with troubleshooting...
Aaand it was the alternator chose that precise moment to die.

Good time to upgrade to the 145 amp version, at least.
 
1 - 17 of 17 Posts
Top