GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC K Sierra - 4WD 🢒 Engine 🢒 Engine Electrical 🢒 Ignition Relay Diagnosis

Object Number: 337600 Size: LF
Engine Controls Component Views
Cell 10: Underhood Bussed Electrical Center, Vehicle Control Module
OBD II Symbol Description Notice

Circuit Description

The IGN relay powers the following components:

    • Injectors/Ignition coils
    • AIR relay

Diagnostic Aids

The following may cause an intermittent:

    • Poor connections. Check for adequate terminal tension. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
    • Corrosion
    • Mis-routed harness.
    • Rubbed through wire insulation.
    • Broken wire inside the insulation.

Test Description

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

  1. Refer to Thumbnail Schematic for proper relay terminal identification.

    2.

  2. This step is testing the relay ground circuit. For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter Kit J 35616 . Using this kit prevents damage to the harness connector terminals. Refer to Using Connector Test Adapters in Wiring Systems.

  3. This step isolates the circuit from the IGN relay. All of the circuits at the relay are good if the test lamp illuminates.

    4.

  4. The open circuit will be between the splice and the IGN relay.

    5.

  5. Remove the underhood electrical center cover and inspect the circuits that are supplied a voltage by the IGN relay.

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 OFF the ignition.
  2. Remove the underhood electrical center cover.
  3. Remove the IGN relay.
  4. Probe the IGN relay B+ feed circuit (switch side of relay) at the underhood electrical center terminal with the test lamp J 35616-200 connected to a ground. Refer to Probing Electrical Connectors in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 3

Go to Step 8

3
  1. Turn ON the ignition leaving the engine OFF.
  2. Probe the IGN relay ignition feed circuit at the underhood electrical center with the test lamp J 35616-200 connected to a ground.

Does the test lamp illuminate?

--

Go to Step 4

Go to Step 9

4

  1. Turn OFF the ignition.
  2. Measure the resistance of the IGN relay ground circuit at the underhood electrical center terminal using the DMM J 39200 connected to the battery ground.

Is the resistance less than the specified value?

0-5ohms

Go to Step 5

Go to Step 10

5

  1. Turn OFF the ignition.
  2. Jumper the IGN relay B+ feed circuit and the IGN relay load circuit together using a fused jumper wire. Refer to Using Fused Jumper Wires in Wiring Systems.
  3. Probe the fuses for the following components with the test lamp J 35616-200 connected to a ground.
    4. • ENG I
    • INJR A
    • INJR B

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 11

6

Inspect for poor terminal contact at the IGN relay underhood electrical center connector. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

Did you find and correct the condition?

--

System OK

Go to Step 7

7

Replace the IGN relay.

Is the action complete?

--

System OK

--

8

Repair the open B+ supply to the IGN relay. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

System OK

--

9

Repair the ignition feed circuit to the IGN relay. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

System OK

--

10

Replace the underhood electrical center. Refer to Underhood Fuse Block Replacement in Wiring Systems.

Is the action complete?

--

System OK

--

11

Replace the Underhood Electrical Center. Refer to Underhood Fuse Block Replacement in Wiring Systems.

Is the action complete?

--

System OK

--