Powertrain Control Module Controlled Warning Lamps Diagnosis Gen. Lamp Control Circuit
Diagnosis
Use the following diagnostic table to diagnose the generator F and L circuit.
Use the following scan tool parameters when diagnosing the PCM controlled generator.
Generator PWM - Range 0-100% : The generator F terminal is a Pulse Width Modulated (PWM) duty cycle or load input to the PCM from the generator. As the generator load increases, the PCM can sense the change and adjust the idle speed accordingly.Generator L Terminal - Range Inactive/Active : The generator L terminal indicates whether the PCM is allowing the generator to operate. The PCM can disable the generator under certain conditions in order to ease starting. Active indicates that the PCM is allowing generator operation, while inactive indicates that the PCM is not allowing generator operation.
Circuit Description
The generator communicates to the Powertrain Control Module (PCM) over two lines, the L orLamp circuit and the F or Field circuit. The PCM uses the L circuit to monitor faults in the charging system. The F circuit is used by the PCM to monitor the duty cycle or load of the generator. The PCM will adjust the idle speed according to the generator load.
Diagnostic Aids
| • | If the generator terminal F input circuit is shorted to voltage, the volts telltale lamp will operate normally. However, the scan tool Generator PWM will display a generator duty cycle near 10%. Check the generator terminal F input circuit for a short to voltage. If OK, the generator may be faulty, refer to the Charging System Diagnosis portion of the service manual. |
| • | An Intermittent problem may be caused by a poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation. |
| • | Any circuitry, that is suspected as causing the intermittent complaint, should be thoroughly checked for the following items: |
| - | Improper mating |
| - | Broken locks |
| - | Poor terminal to wiring connections |
| - | Physical damage to the wiring harness |
Test Description
The number(s) below refer(s) to the step number(s) on the Diagnostic Table.
-
The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the fault occurred. The scan tool stores this data for later reference.
-
If the volts telltale lamp is not operating, the IPC or the BFC is malfunctioning.
-
If no malfunctions are present at this point, refer to Diagnostic Aids for additional checks and information.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
2 | Was a DTC P1601 or P1610 set? | -- | Go to applicable DTC table | |
Turn ON the ignition leaving the engine OFF. Is the volts telltale lamp on the IPC illuminated? | -- | |||
4 | Start the engine. Did the volts telltale lamp on the IPC turn OFF? | -- | ||
5 | Check if any Body Function Controller (BFC) DTCs are set. Are any BFC DTCs set? | -- | Go to Body Function Controller DTC table | Go to Computer System Diagnosis |
Operate the vehicle within the conditions under which the original symptom was observed. Does the system now operate properly? | -- | System OK Refer to Diagnostic Aids |
Powertrain Control Module Controlled Warning Lamps Diagnosis Tachometer Diagnosis
Refer to
Ignition Controls
.
Diagnostic Aids
For diagnosis of the instrument panel, perform the System Check in the Instrument Panel Cluster (IPC) Microprocessor.
Check for the following conditions:
| • | Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. |
| • | Damaged harness. Inspect the wiring harness for damage. |
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
-
Normally, ignition feed voltage should be present on the output driver circuit with the PCM disconnected and the ignition turned on.
-
Checks for a shorted component or a short to battery positive voltage on the output driver circuit. Either conditions would result in a measured current of over 0.5 amps.
-
Checks for a faulty instrument cluster.
-
A fault in the 24X/Camshaft position sensors feed or ground circuits will result in the loss of both PCM input pulses. Without a 24X reference pulse the PCM can not begin tachometer pulse control causing an inoperative tachometer.
-
This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Instrument Cluster diagnosis in Electrical Diagnosis performed? | -- | Refer to Instrument Cluster Diagnosis | |||||||
2 | Was the Powertrain On-Board Diagnostic System Check performed? | -- | ||||||||
Turn off the ignition switch, disconnect the PCM. Turn on the ignition switch. Using J 39200 DMM, measure voltage between the tachometer control circuit at the PCM harness connector and ground. Is voltage near the specified value? | B+ | |||||||||
Set up the DMM to measure 10 amp range. Measure current between the tachometer control circuit and ground. Monitor the current reading on the DMM for at least 2 minutes. Does the current reading remain less than the specified value? | 0.5 Amp | |||||||||
Disconnect the instrument cluster (leave the PCM disconnected). Using the DMM, measure voltage between the tachometer control circuit and ground. Is voltage at the specified value? | 0V | |||||||||
6 | Locate and repair short to voltage in the tachometer control circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||
7 | Check the ignition feed fuse for the instrument cluster. Is the fuse blown? | -- | ||||||||
8 | Locate and repair the following short conditions:
Refer to Fuse Block Details in Electrical Diagnosis. Replace the fuse. Is action complete? | -- | -- | |||||||
9 | Disconnect the instrument cluster. Turn on the ignition switch, measure the voltage between the ignition feed circuit for the instrument cluster and ground. Is voltage near the specified value? | B+ | ||||||||
10 | Check the tachometer control circuit for an open or a short to ground. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis. Was a problem found? | -- | ||||||||
11 | Check the tachometer control circuit and the ignition feed circuit for a poor connection at the instrument cluster and at the PCM. If a problem is found, replace the faulty terminal(s). Refer to Repair Procedures in Electrical Diagnosis. Was a problem found? | -- | ||||||||
12 | Turn off the ignition switch, reconnect the PCM and disconnect the instrument cluster. Connect J 35616-200 test light between the tachometer output control circuit and battery positive voltage at the instrument cluster harness connector. With the engine idling, observe the test light. Does the test light flash on and off ? | -- | Refer to Diagnostic Aids. | |||||||
13 | Is the test light on steady? | -- | ||||||||
Locate and repair the following circuit conditions:
Is action complete? | -- | -- | ||||||||
15 | Check the tachometer control circuit for a poor connection at the PCM. If a problem is found, replace the faulty terminal. Refer to Repair Procedures in Electrical Diagnosis. Was a problem found? | -- | ||||||||
Locate and repair open in the ignition feed circuit to the instrument cluster. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | ||||||||
17 | Replace the instrument cluster. Is action complete? | -- | -- | |||||||
18 | Replace the PCM. Important : Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is action complete? | -- | -- | |||||||
19 | Operate the vehicle while observing the I/P tachometer. Does the I/P tachometer operate properly? | -- | System OK | Refer to Instrument Cluster Diagnosis |
