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Home >> Pontiac >> 2005 >> Grand Prix Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - 3.8L - DTC P0406 To DTC P1111 >> DTC P0685: Engine Controls Ignition Relay Control Circuit >> Diagnostic Aids

Diagnostic Aids

The DTC P0685 diagnostic table assumes that the vehicle battery is fully charged. Refer to Battery Inspection/Test in Engine Electrical.

DTC P0685

Step Action Values Yes No
Schematic Reference: Engine Controls Schematics and Power Distribution Schematics in Wiring Systems
Connector End Views: Powertrain Control Module (PCM) Connector End Views and Electrical Center Identification Views
1 Did you perform the Diagnostic System Check - Vehicle - Go to Step 2  Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2 Attempt to start the engine.
Does the engine start and run?		 - Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems Go to Step 3 
3
  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. NOTE: Refer to Test Probe Notice in Cautions and Notices.
  3. Probe terminal cavity A6 at the underhood fuse block with a test lamp that is connected to a good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.
Does the test lamp illuminate?		 - Go to Step 7  Go to Step 4 
4
  1. Turn ON the ignition, with the engine OFF.
  2. Probe the terminal cavity A6 at the underhood fuse block with a test lamp that is connected to a good ground.
Doe the test lamp illuminate?		 - Go to Step 5  Go to Step 9 
5
  1. Turn OFF the ignition.
  2. Disconnect the powertrain control module (PCM) electrical connector that contains the relay coil control circuit.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe terminal cavity 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 6  Go to Step 12 
6
  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery.
  3. Disconnect the electrical connector that contains the powertrain relay coil control circuit from the underhood fuse block.
  4. Disconnect the powertrain relay coil control circuit terminal from the underhood fuse block electrical connector.
  5. Connect the electrical connector that contains 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 PCM connector with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 - Go to Step 13  Go to Step 15 
7
  1. Turn OFF the ignition.
  2. Disconnect the PCM electrical connector that contains the powertrain relay coil control circuit.
  3. Probe the terminal cavity 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 8  Go to Step 12 
8
  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery.
  3. Disconnect the electrical connector that contains the powertrain relay coil control circuit from the underhood fuse block.
  4. Connect the negative battery cable at the battery.
  5. Probe the powertrain relay coil control circuit wire 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 13  Go to Step 15 
9 Measure the resistance from terminal 30 of the relay to terminal 85 with a DMM.
Does the DMM display the specified value?		 infinityΩ Go to Step 10  Go to Step 14 
10 Measure the resistance from terminal 85 of the relay to terminal 87 with a DMM.
Does the DMM display the specified value?		 infinityΩ Go to Step 11  Go to Step 14 
11 Measure the resistance from terminal 85 of the relay to terminal 86 with a DMM.
Does the DMM display within the specified range?		 70-110 Ω Go to Step 17  Go to Step 14 
12 Test for shorted terminals and poor connections at the PCM.
Did you find and correct the condition?		 - Go to Step 17  Go to Step 16 
13 Repair the short to voltage in the relay coil control circuit.
Did you complete the repair?		 - Go to Step 17  -
14 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 17  -
15 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 17  -
16 Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.
Did you complete the replacement?		 - Go to Step 17  -
17
  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 18  Go to Engine Cranks but Does Not Run
18
  1. Clear the DTCs 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 - Vehicle in Vehicle DTC Information System OK
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