GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 HUMMER 🢒 2006 🢒 H3 🢒 Engine 🢒 Engine Electrical 🢒 Powertrain Relay Diagnosis

Circuit Description

The powertrain relay is a normally open relay. The relay armature is held in the open position by spring tension. Battery positive voltage is supplied directly to the relay coil and the armature contact at all times. The powertrain control module (PCM) supplies the ground path to the relay coil control circuit, via an internal integrated circuit called an output driver module (ODM). When the PCM commands the relay ON, the relay coil creates an electromagnetic field. This electromagnetic field overcomes the spring tension and pulls the armature contact into the stationary contact of the relay load circuit. The closing of the relay contacts allows current to flow from the battery to the following fuses:

    • ETC FUSE
    • O2 SENSOR FUSE

When the ignition switch is turned to the OFF position, the powertrain relay will continue to be energized for 5 seconds after the key is turned OFF. Once the power is interrupted to the output driver module in the PCM, the relay electromagnetic field collapses. This allows the spring tension to separate the relay armature contact from the relay load circuit contact, which interrupts current flow to the fuses.

If the powertrain relay fails to close the engine will crank, but will not run. The PCM class 2 communications will be available with the use of a scan tool.

The powertrain relay system diagnosis table assumes that the vehicle battery if fully charged. Refer to Battery Inspection/Test .

Step

Action

Values

Yes

No

Schematic Reference: Power Distribution Schematics and Engine Controls Schematics

Connector End View References: Power and Grounding Connector End Views , and Electrical Center Identification Views , Powertrain Control Module Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Turn ON the ignition, with the engine OFF.
  2. Remove the underhood fuse block cover.
  3. Probe the following fuses with a test lamp that is connected to a good ground:
    4. • ETC Fuse
    • O2 SENSOR Fuse

Refer to Troubleshooting with a Test Lamp .

Does the test lamp illuminate on at least one test point of each fuse?

--

Go to Step 3

Go to Step 10

3
  1. Turn OFF the ignition.
  2. Probe both test points of the ETC fuse in the underhood fuse block with a test lamp that is connected to a good ground.

Does the test lamp illuminate on either test point of the fuse?

--

Go to Step 4

Go to Step 37

4
  1. Turn OFF the ignition.
  2. Remove the powertrain relay from the underhood fuse block with the J 43244 Relay Puller Pliers. Refer to Relay Replacement .
  3. Probe both the test points of the ETC fuse with a test lamp that is connected to a good ground.

Does the test lamp illuminate on either test point of the fuse?

--

Go to Step 5

Go to Step 7

5
  1. Turn OFF the ignition.
  2. Remove the O2 Sensor fuse from the underhood fuse block.
  3. Probe both test points of the ETC fuse with a test lamp that is connected to a good ground.

Does the test lamp illuminate on either test point of the fuse?

--

Go to Step 6

Go to Diagnostic System Check - Vehicle

6
  1. Turn OFF the ignition.
  2. Remove the ETC fuse from the underhood fuse block.

    3. Notice: Refer to Test Probe Notice in the Preface section.

  3. Probe the powertrain relay load circuit bus bar terminal in the underhood fuse block with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors .

Does the test lamp illuminate?

--

Go to Step 34

Go to Diagnostic System Check - Vehicle

7
  1. Turn OFF the ignition.

    2. Notice: Refer to Test Probe Notice in the Preface section.

  2. Probe the powertrain relay coil control circuit terminal in the underhood fuse block with a test lamp that is connected to battery positive voltage. Refer to Probing Electrical Connectors .

Does the test lamp illuminate?

--

Go to Step 8

Go to Step 23

8
  1. Turn OFF the ignition.
  2. Disconnect the powertrain control module (PCM) electrical connector that contains the relay coil control circuit. Refer to Powertrain Control Module Replacement .
  3. Probe the powertrain relay coil control circuit terminal in the underhood fuse block with a test lamp this is connected to battery positive voltage.

Does the test lamp illuminate?

--

Go to Step 9

Go to Step 30

9
  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnection and Connection .
  3. Disconnect the underhood fuse block electrical connector that contains the powertrain relay coil control circuit. Refer to Underhood Electrical Center or Junction Block Replacement .
  4. Probe the powertrain relay coil control circuit at the underhood fuse block electrical connector with a test lamp that is connected to battery positive voltage.

Does the test lamp illuminate?

--

Go to Step 31

Go to Step 34

10
  1. Turn OFF the ignition.
  2. Remove the powertrain relay from the underhood fuse block with the J 43244 . Refer to Relay Replacement .

    3. Notice: Refer to Test Probe Notice in the Preface section.

  3. Probe the battery positive voltage terminal for the powertrain relay coil in the underhood fuse block with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors .

Does the test lamp illuminate?

--

Go to Step 12

Go to Step 11

11

Probe the mounting stud for the positive battery cable at the underhood fuse block with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 34

Go to Diagnostic System Check - Vehicle

12
  1. Turn OFF the ignition.
  2. Probe the powertrain relay coil control circuit terminal in the underhood fuse block with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 16

Go to Step 13

13
  1. Turn ON the ignition, with the engine OFF.
  2. Probe the powertrain relay coil control circuit terminal in the underhood fuse block with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 14

Go to Step 18

14
  1. Turn OFF the ignition.
  2. Disconnect the PCM electrical connector that contains the relay coil control circuit. Refer to Powertrain Control Module Replacement .
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the powertrain relay coil control circuit at the underhood fuse block with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 15

Go to Step 30

15
  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnection and Connection .
  3. Disconnect the underhood fuse block electrical connector that contains the powertrain relay coil control circuit. Refer to Underhood Electrical Center or Junction Block Replacement .
  4. Disconnect the powertrain relay coil connector circuit terminal from the underhood fuse block electrical connector. Refer to Delphi Connectors .
  5. Connect the electrical connector that contained the powertrain relay coil control circuit to the underhood fuse block.
  6. Connect the negative battery cable at the battery.
  7. Turn ON the ignition, with the engine OFF.
  8. Probe the powertrain relay coil control circuit terminal at the underhood fuse block electrical connector with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 32

Go to Step 34

16
  1. Turn OFF the ignition.
  2. Disconnect the PCM electrical connector that contains the powertrain relay coil control circuit. Refer to Powertrain Control Module Replacement .
  3. Probe the powertrain relay coil control circuit terminal in the underhood fuse block with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 17

Go to Step 30

17
  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnection and Connection .
  3. Disconnect the underhood fuse block electrical connector that contains the powertrain relay coil control circuit. Refer to Underhood Electrical Center or Junction Block Replacement .
  4. Connect the negative battery cable at the battery.
  5. Probe the powertrain relay coil connector circuit at the underhood fuse block electrical connector with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 32

Go to Step 34

18
  1. Turn OFF the ignition.
  2. Probe the battery positive voltage terminal for the powertrain relay armature at the underhood fuse block with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 19

Go to Step 34

19
  1. Turn ON the ignition, with the engine OFF.

    2. Notice: Refer to Test Probe Notice in the Preface section.

  2. Probe the powertrain relay coil control circuit terminal at the underhood fuse block with a test lamp that is connected to battery positive voltage.

Does the test lamp illuminate?

--

Go to Step 22

Go to Step 20

20
  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnection and Connection .
  3. Disconnect the underhood fuse block electrical connector that contains the powertrain relay coil control circuit. Refer to Underhood Electrical Center or Junction Block Replacement .
  4. Disconnect the PCM electrical connector that contains the powertrain relay coil control circuit. Refer to Powertrain Control Module Replacement .
  5. Measure the resistance of the powertrain relay coil control circuit from the underhood fuse block electrical connector to the PCM electrical connector with a DMM. Refer to Troubleshooting with a Digital Multimeter .

Does the resistance measure greater than the specified value?

5 ohms

Go to Step 33

Go to Step 21

21

Test the powertrain relay coil control bus bar circuit of the underhood fuse block for a high resistance or an open. Refer to Circuit Testing .

Did you find a condition?

--

Go to Step 34

Go to Step 30

22
  1. Turn OFF the ignition.
  2. Connect a 20-amp fused jumper wire between the battery positive voltage circuit terminal of the underhood fuse block and the relay load circuit terminal of the underhood fuse block. Refer to Using Fused Jumper Wires .
  3. Probe the following fuses with a test lamp that is connected to a good ground:
    4. • ETC fuse
    • O2 SENSOR fuse

Does the test lamp illuminate on at least one test point of each fuse?

--

Go to Step 23

Go to Step 34

23

Measure the resistance from terminal #85 of the relay to terminal #86 with a DMM. Refer to Troubleshooting with a Digital Multimeter .

Does the resistance measure within the specified range?

70-110 ohms

Go to Step 24

Go to Step 35

24

Measure the resistance from terminal #30 of the relay to terminal #87 with a DMM. Refer to Troubleshooting with a Digital Multimeter .

Does the DMM display the specified value?

∞ ohms

Go to Step 25

Go to Step 35

25

Measure the resistance from terminal #30 of the relay to terminal #85 with a DMM. Refer to Troubleshooting with a Digital Multimeter .

Does the DMM display the specified value?

∞ ohms

Go to Step 26

Go to Step 35

26

Measure the resistance from terminal #85 of the relay to terminal #87 with a DMM. Refer to Troubleshooting with a Digital Multimeter .

Does the DMM display the specified value?

∞ ohms

Go to Step 27

Go to Step 35

27

Measure the resistance from terminal #86 of the relay to terminal #87 with a DMM. Refer to Troubleshooting with a Digital Multimeter .

Does the DMM display the specified value?

∞ ohms

Go to Step 28

Go to Step 35

28
  1. Connect a 20-amp fused jumper wire from the battery positive cable at the battery to relay terminal #85. Refer to Using Fused Jumper Wires .
  2. Connect a jumper wire from the negative battery cable to the relay terminal #86.
  3. Measure the resistance from terminal #30 of the relay to terminal #87 with a DMM.

Does the resistance measure more than the specified value?

3 ohms

Go to Step 35

Go to Step 29

29

Test for an intermittent and for a poor connection at the powertrain relay location on the underhood fuse block. Refer to Testing for Intermittent Conditions and Poor Connections .

Did you find a condition?

--

Go to Step 34

Go to Testing for Intermittent Conditions and Poor Connections

30

Test for shorted terminals and poor connections at the PCM electrical connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 37

Go to Step 36

31

Repair the short to ground in the relay coil control circuit between the underhood fuse block and the PCM. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 37

--

32

Repair the short to voltage in the relay coil control circuit between the underhood fuse block and the PCM. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 37

--

33

Repair the high resistance or an open in the relay coil control circuit between the underhood fuse block and the PCM. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 37

--

34

Replace the underhood fuse block. Refer to Underhood Electrical Center or Junction Block Replacement .

Did you complete the replacement?

--

Go to Step 37

--

35

Replace the powertrain relay. Refer to Relay Replacement .

Did you complete the replacement?

--

Go to Step 37

--

36

Replace the PCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 37

--

37
  1. Reassemble the vehicle as necessary.
  2. Replace any open fuses.
  3. Clear any DTCs with a scan tool.
  4. Start the engine.
  5. Operate the vehicle in order to verify the repair.

Did you correct the condition?

--

Go to Step 38

Go to Engine Cranks But Does Not Run

38

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK