GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC C Sierra - 2WD 🢒 Engine 🢒 Engine Controls - 4.8L, 5.3L, and 6.0L 🢒 Ignition Relay Diagnosis

Circuit Description

The ignition relay supplies battery positive voltage to the following components:

    • The fuel injectors
    • The ignition coils
    • The powertrain control module (PCM)
    • The throttle actuator control (TAC) module

Diagnostic Aids

The following will occur if the ignition relay fails to close:

    • The engine cranks, but does not run.
    • Scan tool data will be available.
    • Instrument panel lights will illuminate.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step is testing the battery positive voltage circuit of the ignition relay.

    2.

  2. This step is testing the ignition 1 positive voltage circuit of the ignition relay.

    3.

  3. This step is testing the coil ground circuit of the ignition relay.

    4.

  4. This step isolates the circuits from the ignition relay. All of the circuits at the relay are good if the test lamp illuminates.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics and Ground Distribution Schematics in Wiring Systems.

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Turn OFF the ignition.
  2. Remove the underhood fuse block cover.
  3. Remove the ignition relay with the J 43244 Relay Puller Pliers.
  4. Probe the battery positive voltage circuit for the ignition relay at the underhood fuse block with a test lamp connected to a good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp illuminate?

Go to Step 3

Go to Step 10

3

  1. Turn ON the ignition, with the engine OFF.
  2. Probe the ignition 1 voltage circuit for the ignition relay at the underhood fuse block with a test lamp connected to a good ground.

Does the test lamp illuminate?

Go to Step 4

Go to Step 6

4

  1. Turn ON the ignition, with the engine OFF.
  2. Probe the coil ground circuit for the ignition relay at the underhood fuse block with a test lamp connected to battery voltage.

Does the test lamp illuminate?

Go to Step 5

Go to Step 7

5

  1. Turn OFF the ignition.
  2. Jumper the ignition relay battery positive voltage circuit and the ignition relay load circuit together, at the underhood fuse block, with a fused jumper wire. Refer to Using Fused Jumper Wires in Wiring Systems.

    3. Important: At least one test point of each fuse must illuminate the test lamp.

  3. Probe the following fuses with a test lamp connected to a good ground.
    4. • ECM I
    • INJ A
    • INJ B

Does the test lamp illuminate?

Go to Step 8

Go to Step 10

6
  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
  3. Disconnect the underhood fuse block electrical connectors.
  4. Test the ignition 1 voltage circuit of the ignition relay at the underhood fuse block electrical connector for an open circuit or for a short to ground. Refer to Circuit Testing in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 10

7
  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
  3. Disconnect the underhood fuse block electrical connectors.
  4. Test the coil ground circuit of the ignition relay at the underhood fuse block electrical connector for a high resistance or for an open circuit. Refer to Testing for Continuity in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 10

8

Inspect for poor terminal contact at the ignition relay connector position of the underhood fuse block. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find a condition?

Go to Step 10

Go to Step 9

9

Replace the ignition relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 11

--

10

Important: Do not dissemble or attempt any repairs to the underhood fuse block.

Replace the underhood electrical center. Refer to Underhood Electrical Center or Junction Block Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 11

--

11
  1. Clear the DTCs with a scan tool.
  2. Turn ignition OFF for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle for 5 minutes.

Does the vehicle operate normally, with no malfunction indicator lamp (MIL) illumination and no stored DTCs?

System OK

Go to Diagnostic Trouble Code (DTC) List