GM Service Manual Online
For 1990-2009 cars only

Refer to

AIR ,Gen Control Volts Lamp, Low Oil


Object Number: 23128  Size: FS
Engine Controls Components
Information Sensors
HAVOC A/C Control
TCC, Brake Switch
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
and

PCM Power, Grounds, MIL Control, Serial Data


Object Number: 23095  Size: FS
Engine Controls Components
Data Link Connector Diagnosis
Ignition Control
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Wiring Schematics.

Circuit Description

The Engine Oil Level Switch is a simple float switch that is grounded when the engine oil level is OK. The PCM checks the Engine Oil Level switch circuit at startup. Before checking the state of the Engine Oil Level switch, the PCM performs a test routine based on time and engine coolant temperature to ensure that the engine oil has drained back into the sump. 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 140°C (284°F) at the last key OFF, the engine coolant temperature 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 temperature was higher than 140°C (284°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 remain powered up for 15 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.

The Low Oil Level Lamp will be illuminated for about a minute when the PCM checks 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). 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.

Diagnostic Aids

For diagnosis of the instrument panel, perform the System Check in the Instrument Cluster section of Electrical Diagnosis.

Check for the following conditions:

    • Poor connection at PCM or oil level sensor. 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 Sensor circuit: If the problem with the Low Oil Level lamp can not be isolated using Engine Oil Level Switch diagnostic table, use PCM Controlled Lamps diagnostic table.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Chart.

  1. Normally, ignition feed voltage should be present on the output driver circuit with the PCM disconnected and the ignition turned ON.

  2. Checks for a shorted component or a short to B+ on the output driver 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.

  3. Checks for a faulty instrument cluster.

  4. 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.

PCM Controlled Lamps

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to the Powertrain On Board Diagnostic (OBD) System Check

2

Was the instrument cluster system check in Electrical Diagnosis performed?

--

Go to Step 3

Go to Electrical Diagnosis

3

  1. Turn OFF the ignition switch, disconnect the PCM.
  2. Turn ON the ignition switch.
  3. Using J 39200 digital voltmeter (DVM), measure voltage between the affected PCM output circuit at the PCM harness connector and ground.

Is voltage near the specified value?

B+

Go to Step 4

Go to Step 7

4

  1. Set up DVM to measure 10 amp range.
  2. Measure current between the affected PCM output circuit and ground.
  3. Monitor the current reading on the DVM for at least 2 minutes.

Does the current reading remain between the specified values?

0.05 Amp 1.5 Amps

Go to Step 12

Go to Step 5

5

  1. Disconnect the instrument panel cluster (leave the PCM disconnected).
  2. Using DVM, measure voltage between the affected PCM output circuit and ground.

Is voltage at the specified value?

0V

Go to Step 15

Go to Step 6

6

Locate and repair short to voltage in affected PCM output circuit.

Is action complete?

--

Go to Step 17

--

7

Check the ignition feed fuse for the instrument panel cluster indicator lamps.

Is the fuse blown?

--

Go to Step 8

Go to Step 9

8

  1. Locate and repair short to ground in ignition feed circuit for the instrument panel cluster indicator lamps. Refer to Fuse Block Details in Electrical Diagnosis.
  2. Replace fuse.

Is action complete?

--

Go to Step 17

--

9

  1. Disconnect the instrument panel cluster.
  2. Turn ON the ignition switch, measure voltage between the ignition feed circuit for the instrument panel cluster indicator lamps and ground.

Is voltage near the specified value?

B+

Go to Step 10

Go to Step 14

10

  1. Check the affected PCM output circuit for an open or a short to ground.
  2. If a problem is found, repair the affected PCM output circuit. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 17

Go to Step 11

11

  1. Check the affected PCM output circuit and the ignition feed circuit for a poor connection at the instrument panel cluster and at the PCM.
  2. If a problem is found, replace faulty terminal(s). Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 17

Go to Step 15

12

  1. Turn OFF the ignition switch, reconnect the PCM and disconnect the instrument panel cluster.
  2. Turn ON the ignition switch, connect a test light between the affected PCM output circuit and the ignition feed circuit at the instrument panel cluster harness connector.
  3. Using the scan tool outputs test function, cycle the affected lamp ON and OFF.

Does the test light flash ON and OFF?

--

Refer to Diagnostic Aids

Go to Step 13

13

  1. Check the affected PCM output circuit for a poor connection at the PCM.
  2. If a problem is found, replace faulty terminal. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 17

Go to Step 16

14

Locate and repair open in ignition feed circuit to the instrument panel cluster indicator lamps Refer to Repair Procedures in Electrical Diagnosis.

Is action complete?

--

Go to Step 17

--

15

Replace the instrument panel cluster.

Is action complete?

--

Go to Step 17

--

16

Replace the PCM.

Important: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .

Is action complete?

--

Go to Step 17

--

17

Operate the affected lamp using the scan tool output tests function.

Does the affected lamp operate properly?

--

System OK

Go to Step 2