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Circuit Description

WARNING: This page is about a different car, the 2004 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.

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. 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 allow current to flow from the battery to the following fuses:

When the ignition switch is turned to the OFF position, power is interrupted to the output driver module in the PCM, and the relay electromagnetic field collapses. This action allows the spring tension pulling on the armature to separate 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 class 2 communications will be available with the use of a scan tool.

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

Powertrain Relay Diagnosis

Step Action Values Yes No
Schematic Reference: Engine Controls Schematics and Power Distribution Schematics in Wiring Systems
Connector End View Reference: Powertrain Control Module (PCM) Connector End Views and Electrical Center Identification Views
1 Did you perform the Diagnostic System Check-Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2 Is DTC P0685 set? - Go to Diagnostic Trouble Code (DTC) List Go to Step 3 
3
  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. Refer to Troubleshooting with a Test Lamp in Wiring Systems.
    • ECT Fuse
    • ELEK IGN Fuse
    • FUEL INJ Fuse
    • O2 SSR Fuse
    • EMISSION Fuse
Does the test lamp illuminate on at least one test point of each fuse?		 - Go to Step 4  Go to Step 14 
4
  1. Turn OFF the ignition.
  2. Probe both test points of the 10-amp EMISSION 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 5  Go to Step 33 
5
  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 (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems.
  3. Probe both test points of the 10-amp EMISSION 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 9  Go to Step 6 
6
  1. Turn OFF the ignition.
    2. NOTE: Refer to Test Probe Notice in Cautions and Notices.
  2. Probe terminal cavity A6 at the underhood fuse block with a test lamp that is connected to battery positive voltage.
Does the test lamp illuminate?		 - Go to Step 7  Go to Step 21 
7
  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnect/Connect Procedure in Engine Electrical.
  3. Disconnect the electrical connector that contains the powertrain relay coil control circuit from the underhood fuse block.
  4. Disconnect the PCM electrical connector that contains the powertrain relay coil control circuit from the PCM.
  5. Probe the powertrain relay coil control circuit at the PCM electrical connector with a test lamp that is connected to battery positive voltage.
Does the test lamp illuminate?		 - Go to Step 28  Go to Step 8 
8 Test the powertrain relay coil control bus bar circuit in the underhood fuse block for a short to ground. Refer to Circuit Testing in Wiring Systems.
Did you find a condition?		 - Go to Step 32  Go to Step 26 
9
  1. Turn OFF the ignition.
  2. Remove the ECT fuse from the underhood fuse block.
  3. Probe both test points at the 10-amp EMISSION 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 10  Go to Diagnostic System Check - Engine Electrical in Engine Electrical
10
  1. Turn OFF the ignition.
  2. Remove the ELEK IGN fuse from the underhood fuse block.
  3. Probe both test points at the 10-amp EMISSION 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 11  Go to Diagnostic System Check - Engine Electrical in Engine Electrical
11
  1. Turn OFF the ignition.
  2. Remove the FUEL INJ fuse from the underhood fuse block.
  3. Probe both test points at the 10-amp EMISSION 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 12  Go to Diagnostic System Check - Engine Electrical in Engine Electrical
12
  1. Turn OFF the ignition.
  2. Remove the O2 SSR fuse from the underhood fuse block.
  3. Probe both test points at the 10-amp EMISSION 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 13  Go to Diagnostic System Check - Engine Electrical in Engine Electrical
13
  1. Turn OFF the ignition.
  2. Remove the EMISSION fuse from the underhood fuse block.
    3. NOTE: Refer to Test Probe Notice in Cautions and Notices.
  3. Probe terminal A6 at the underhood fuse block with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 - Go to Step 32  Go to Diagnostic System Check - Engine Electrical in Engine Electrical
14
  1. Turn OFF the ignition.
  2. Remove the powertrain relay from the underhood fuse block with a J 43244  . Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems.
    3. NOTE: Refer to Test Probe Notice in Cautions and Notices.
  3. Probe terminal C6 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 19 
15
  1. Turn OFF the ignition.
  2. Probe terminal C5 at 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 19 
16
  1. Turn ON the ignition, with the engine OFF.
  2. Probe terminal cavity A6 at the underhood fuse block with a test lamp that is connected to battery positive voltage.
Does the test lamp illuminate?		 - Go to Step 20  Go to Step 17 
17
  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnect/Connect Procedure in Engine Electrical.
  3. Disconnect the electrical connector that contains the powertrain relay coil control circuit from the underhood fuse block.
  4. Disconnect the PCM electrical connector that contains the powertrain relay coil control circuit from the PCM.
  5. Measure the resistance of the powertrain relay coil control circuit with a DMM. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems.
Does the resistance measure greater than the specified value?		 5 Ω Go to Step 29  Go to Step 18 
18 Test the underhood fuse block powertrain relay coil control bus bar circuit for a high resistance or an open. Refer to Circuit Testing in Wiring Systems.
Does the resistance measure greater than the specified value?		 5 Ω Go to Step 32  Go to Step 27 
19 Probe the mounting stud for the battery positive cable at the underhood fuse block with a test lamp that is connected to a good ground.
Does the lamp illuminate?		 - Go to Step 32  Go to Diagnostic System Check - Engine Electrical in Engine Electrical
20
  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 (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) In Wiring Systems.
  3. Connect terminal cavity C6 to terminal cavity A5 together at the underhood fuse block with a 20-amp fused jumper wire. Refer to Using Fused Jumper Wires in Wiring Systems.
  4. Probe the following fuses with a test lamp that is connected to a good ground.
    • ETC Fuse
    • ELEK IGN Fuse
    • FUEL INJ Fuse
    • O2 SSR Fuse
    • Emission Fuse
Does the test lamp illuminate on at least one test point of each fuse?		 - Go to Step 21  Go to Step 32 
21 Measure the resistance from terminal #85 of the relay to terminal #86 with a DMM. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems.
Does the resistance measure within the specified value?		 70-110 Ω Go to Step 22  Go to Step 30 
22 Measure the resistance from terminal #30 of the relay to terminal #87 with a DMM. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems.
Does the DMM display the specified value?		 infinityΩ Go to Step 23  Go to Step 30 
23 Measure the resistance from terminal #30 of the relay to terminal #85 with a DMM. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems.
Does the DMM display the specified value?		 infinityΩ Go to Step 24  Go to Step 30 
24 Measure the resistance from terminal #85 of the relay to terminal #87 with a DMM. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems.
Does the DMM display the specified value?		 infinityΩ Go to Step 25  Go to Step 30 
25
  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 in Wiring Systems.
  2. Connect a jumper wire from the negative battery cable at the battery to 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 Ω Go to Step 30  Go to Intermittent Conditions 
26 Test for shorted terminals and poor connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 33  Go to Step 31 
27 Test for intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 33  Go to Step 31 
28 Repair the short to ground in the powertrain relay coil control circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 33  -
29 Repair the high resistance or an open in the powertrain relay coil control circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 33  -
30 Replace the powertrain relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems.
Did you complete the replacement?		 - Go to Step 33  -
31 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Did you complete the replacement?		 - Go to Step 33  -
32 Replace the underhood fuse block. Refer to Underhood Electrical Center or Junction Block Replacement in Wiring Systems.
Did you complete the replacement?		 - Go to Step 33  -
33
  1. Reassemble the vehicle as necessary.
  2. Replace any open fuses.
  3. Turn OFF the ignition for 30 seconds.
  4. Attempt to start the engine.
Does the engine start and run?		 - Go to Step 34  Go to Engine Cranks but Does Not Run 
34
  1. Clear the DTC with a scan tool.
  2. Operate the vehicle for 5 minutes.
Does a DTC set during this ignition cycle?		 - Go to Diagnostic Trouble Code (DTC) List System OK
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