Circuit Description
The PCM controlled lamps and gauge(s) are powered through an IGN 1 fuse. The PCM energizes the the bulb, LED, guage, or driver information center indicator by supplying a path to ground through the PCM.
Conditions which will illuminate each lamp are as follows:
| • | Low Oil Level Lamp-- will be illuminated for about a 7 minutes after the ignition has been turned ON when the PCM tests for low oil level and the engine oil level switch indicates that a low oil level condition exists (Engine Oil Level Switch circuit not grounded). The PCM determines whether or not to test for low oil level based on the difference between engine coolant temperature at the last shutdown and engine coolant temperature at startup. This is to ensure that the oil has drained back into the sump before testing. When the ignition is first turned ON, the PCM commands the Low Oil Level lamp ON for a brief period of time to test the bulb. To test for low oil level at startup, one of the following conditions must be present: |
| - | If the engine coolant temperature was between 15°C (59°F) and 130°C (266°F) at the last key OFF, the engine coolant termperature at key ON must be at least 12°C (22°F) cooler than the engine coolant temperature at the last key OFF. |
| - | If the engine coolant termperature was higher than 82°C (180°F) at the last key OFF, the time between last key OFF and the present key ON must be sufficient to allow the oil to drain back to the sump. The PCM will remian powered up for 10 seconds to ensure that the oil has drained back to the sump. If the key is turned back ON while the PCM is still powered up, the oil level will not be tested. |
| • | Generator Lamp--The PCM supplies battery voltage to the generator's internal regulator (generator terminal L). When a fault in the Charging System occurs, the internal regulator grounds the L terminal voltage and the PCM commands the generator lamp ON. The PCM will command the generator lamp ON when the following condition(s) are present: |
| - | Engine speed is above 1200 RPM and system voltage is below 10 volts for at least 10 seconds. |
| - | The PCM detects a low voltage condition on the generator's L terminal for at least 10 seconds. |
| • | Change Oil Lamp--The PCM uses the number of engine revolutions to calculate a percentage of remaining engine oil life. If the PCM detects a remaining oil life of 11 percent, the Change Oil Lamp will be illuminated. The Change Oil Lamp will remain illuminated for 60 seconds after the ignition switch is turned on. |
Fuel Level Gauge-- The PCM uses the fuel level sensor information to control the fuel gauge via the fuel level output control circuit. The PCM supplies 5 volts to the fuel level sensor circuit. The fuel level sensor varies the voltage relative to the amount of fuel in the tank. The PCM monitors the voltage on the fuel level circuit to calculate the amount of fuel in the tank. If a malfunction occurs in the fuel level output control circuit, DTC P1653 will set.
Diagnostic Aids
A PCM controlled lamp ON at all times most likely indicates that a condition is present which requires the attention of the vehicle operator.
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. If the harness appears to be OK, disconnect the PCM and turn the ignition ON. Observe a voltmeter connected to the affected PCM output circuit while moving connectors and wiring harnesses related to the PCM output circuit. A change in voltage will indicate the location of the fault. |
| • | Engine Oil Level Switch circuit. |
| • | Fuel Level Output Control Circuit: Refer to DTC P1653 Fuel Level Output Circuit . |
Test Description
The numbers below refer to the step numbers on the diagnostic yable.
-
Normally, ignition feed voltage should be present on the output control circuit with the PCM disconnected and the ignition turned ON.
-
Checks for a shorted component or a short to B+ on the output control circuit. Either condition would result in a measured current of over 1.5 amps. Also checks for a component that is going open while being operated, resulting in a measured current of 0 amps.
-
Checks for a malfunctioning instrument cluster.
-
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.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 | Was the Instrument Cluster System Check performed? | -- | ||
Is voltage near the specified value? | B+ | |||
Does the current reading remain between the specified values? | 0.05 Amp-1.5 Amps | |||
Is voltage at the specified value? | 0V | |||
6 | Locate and repair the short to voltage in the affected PCM output circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
7 | Check the Ignition feed fuse for the instrument panel cluster indicator lamps. Is the the fuse blown? | -- | ||
8 |
Did you complete the repair? | -- | -- | |
9 |
Is voltage near the specified value? | B+ | ||
10 |
Was a problem found? | -- | ||
11 |
Was a problem found? | -- | ||
12 |
Does the test lamp flash ON and OFF? | -- | Go to Diagnostic Aids | |
13 |
Was a problem found? | -- | ||
14 | Locate and repair open in the Ignition feed circuit to the instrument panel cluster indicator lamps. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
15 | Replace the instrument panel cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Gauges and Console. Did you complete the repair? | -- | -- | |
|
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the repair? | -- | -- | ||
17 | Operate the affected lamp using the scan tool output tests function. Does the affected lamp operate properly? | -- | System OK |
