GM Service Manual Online
For 1990-2009 cars only

Refer to

PWR, GND, and DLC


Object Number: 185277  Size: FS
Cell 10: Battery, and Underhood Fuse Block
Cell 10: LIGHTING and BATTERY Fuses
Cell 10: IGN A Fuse and Ignition Switch
Cell 10: LIGHTING and BATTERY Fuses
Cell 10: ECM-B, HORN and A/C COMP Fuses
Cell 10: ENG 1 and ECM 1 Fuses (Diesel)
Cell 10: GAUGES Fuse
Powertrain Control Module Connector End Views
Cell 11: G104 Diesel
Cell 11: G104 Diesel
Cell 14: G200 (1 of 4)
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
OBD II Symbol Description Notice
Fuel Controls
.

Circuit Description

There should always be a malfunction indicator lamp (MIL) when the ignition is ON and the engine is OFF. Battery ignition voltage is supplied to the lamp. The PCM will turn the lamp ON by grounding the ignition feed circuit.

Test Description

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

  1. This step verifies if the problem is in the scan tool or the vehicle.

  2. This step will check the ground circuits at the DLC connector.

  3. The step will check for the battery and ignition feeds to the PCM.

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

  1. Turn ON the ignition with the engine OFF.
  2. Connect the scan tool to the DLC.

Does the scan tool power-up?

--

Go to Step 3

Go to Step 5

3

  1. Turn OFF the ignition for 15 seconds.
  2. Attempt to start the vehicle.

Does the engine start then stall?

--

Go to Content Theft Deterrent (CTD) Circuit Description

Go to Step 4

4

Did the engine just crank over and not start?

--

Go to Step 9

Go to Step 13

5

  1. Disconnect the scan tool from the DLC.
  2. Turn ON the ignition with the engine OFF.
  3. Probe the DLC terminal 16 using an J 35616-200 unpowered test lamp connected to battery ground.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 16

6

Probe the DLC terminals 4 and 5 using an J 35616-200 unpowered test lamp connected to B+.

Does the test lamp illuminate on both circuits?

--

Go to Step 7

Go to Step 8

7

  1. Inspect the scan tool connections to the DLC.
  2. Also inspect the terminals for proper tension at the DLC. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

8

Repair the open ground circuit to the DLC terminals 4 and 5. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

9

  1. Turn OFF the ignition.
  2. Disconnect the PCM connector containing the Battery and Ignition feed circuits.
  3. Turn ON the ignition.
  4. Probe the Battery and Ignition feed circuits in the PCM harness connectors with a test lamp connected to battery ground.

Does the test lamp illuminate on each circuit?

--

Go to Step 10

Go to Step 14

10

Measure the resistance between the battery ground and the PCM ground circuits in the PCM harness connectors using a J 39200 DMM.

Does the DMM display the specified value (or lower) on each circuit?

5 ohms

Go to Step 11

Go to Step 15

11

Inspect the PCM for proper connections. Refer to Wiring Repairs in Wiring Systems.

Did you perform a repair?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 12

12

Replace the PCM.

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

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

13

Repair the Class 2 circuit for being open between the splice and the DLC. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

14

Repair the circuit that did not illuminate the test lamp. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

15

Repair the PCM ground circuit(s). Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

16

Repair the B+ supply circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--