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Diagnostic Aids

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 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 - in Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2 Attempt to start the engine.
Does the engine start and run?		 - Go to Intermittent Conditions 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. Refer to Powertrain Control Module (PCM) Replacement .
  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. 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. Refer to Underhood Electrical Center or Junction Block Replacement in Wiring Systems.
  4. Disconnect the powertrain relay coil control circuit terminal from the underhood fuse block electrical connector. Refer to Push to Seat Connectors in Wiring Systems.
  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. Refer to Probing Electrical Connectors in Wiring Systems.
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. Refer to Powertrain Control Module (PCM) Replacement .
  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. 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. Refer to Underhood Electrical Center or Junction Block Replacement in Wiring Systems.
  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. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems.
Does the DMM display the specified value?		 infinityohm 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?		 infinityohm 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 ohm Go to Step 17  Go to Step 14 
12 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 17  Go to Step 16 
13 Repair the short to voltage in the relay coil control circuit. Refer to Wiring Repairs in Wiring Systems.
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 Powertrain Control Module (PCM) Replacement .
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 System OK
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