DTC P1637 Generator L-Terminal
Circuit
The L-terminal circuit
from the generator is a discrete circuit (a discrete circuit has no splices and
only one source and one destination) into the PCM. The PCM applies ignition
voltage to the generator L terminal circuit. A small amount
of current flows from this circuit through the generator windings to create a
magnetic field which starts the generator process. When the generator is
at operating speed and producing voltage, a solid state switch for the L
terminal circuit in the generator opens and the PCM detects that the initial
startup current flow has stopped.
The PCM expects to
detect low voltage on the L terminal circuit prior to the generator rotating at
operating speed and conversely expects the circuit to be at ignition voltage
potential when the generator is operational. When the PCM detects a fault
(circuit shorted to ground, or circuit shorted to a voltage), this DTC will
set.
Conditions
for Running the DTC
Engine
operating.
Conditions
for Setting the DTC
The PCM detects an
improper voltage on the generator L terminal circuit.
Action
Taken When the DTC Sets
- The PCM stores the DTC information
into memory when the diagnostic runs and fails.
- The malfunction indicator lamp (MIL)
will not illuminate.
- The PCM records the operating
conditions at the time the diagnostic fails. The PCM stores this
information in the Failure Records.
Conditions
for Clearing the DTC
- A last test failed, or current DTC,
clears when the diagnostic runs and does not fail.
- A history DTC will clear after
40 consecutive warm-up cycles, if no failures are reported by this or
any other non-emission related diagnostic.
- Use a scan tool in order to clear
the DTC.
Important
- Remove any debris from the PCM connector surfaces
before servicing the PCM. Inspect the PCM connector gaskets when
diagnosing/replacing the PCM. Ensure that the gaskets are installed
correctly. The gaskets prevent water intrusion into the PCM.
- For any test that requires probing the PCM or component
harness connectors, use the J 35616-A
connector test adapter kit. Using this kit prevents damage to the harness
connector terminals. Refer to Using
Connector Test Adapters in Wiring Systems.
A generator fault, such
as a shorted output diode, malfunctioning regulator, open or shorted rotor, or
open sense lead may cause a low battery charge. Refer to A
Diagnostic Starting Point - Engine Electrical in Engine Electrical for
further information and generator diagnosis.
Use a scan tool in order
to diagnosis the generator circuits. A scan tool displays Generator L-Terminal
Inactive when there is a concern with the L-terminal circuit.
For an intermittent
condition, refer to Symptoms
.
The numbers below refer
to the step numbers on the Diagnostic Table.
|
Step |
Action |
Value(s) |
Yes |
No |
|
Did
you perform the Powertrain On-Board Diagnostic
(OBD) System Check? |
-- |
|||
Does
the scan tool display the Generator L terminal as Inactive? |
-- |
Go to Diagnostic Aids |
||
|
Probe
the Generator battery feed circuit using the J 34142-B test
lamp connected to ground. Refer to Probing
Electrical Connectors in Wiring Systems. Does the test lamp illuminate? |
-- |
Go to A
Diagnostic Starting Point - Engine Electrical in Engine Electrical |
||
Is
the voltage the same or more than the value specified? |
10V |
|||
Does
the DMM indicate continuity? |
-- |
|||
|
Test
for continuity from terminal B at the generator harness connector to battery
ground using the DMM. Refer to Testing
for Continuity in Wiring Systems. Does the DMM indicate continuity? |
-- |
|||
|
Repair
the short to ground in the generator circuit. Refer to Wiring
Repairs in Wiring Systems. Is the repair complete? |
-- |
-- |
||
|
Repair
the open/high resistance in the generator circuit. Refer to Wiring
Repairs in Wiring Systems. Is the repair complete? |
-- |
-- |
||
Did
you find and correct the condition? |
-- |
|||
|
Important: Program the replacement PCM.
Refer to PCM
Replacement/Programming . Replace
the PCM. Is the action complete? |
-- |
-- |
||
Did
you find and correct the condition? |
-- |
|||
|
Replace
the generator. Refer to Generator
Replacement in Engine Electrical. Is the action complete? |
-- |
-- |
||
Does
the scan tool indicate that this test ran and passed? |
-- |
|||
|
Select
the Capture Info option and the Review Info option using the scan tool. Does
the scan tool display any DTCs that you have not diagnosed? |
-- |
Go to the applicable
DTC table |
System OK |