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 engine control module (ECM) supplies the ground path to the relay coil control circuit via an internal integrated circuit called an output driver module (ODM). One ODM output control is configured to operate as a low side driver for the powertrain relay. The ODM for the powertrain relay also incorporates a fault detection circuit, which is continuously monitored by the ECM. When the ECM commands the ODM for the powertrain relay to turn OFF, the expected voltage on the relay coil control circuit should be a high voltage condition. When the ECM commands the ODM to turn ON, the expected voltage on the relay coil control circuit should be a low voltage condition. DTC P0685 indicates that the powertrain relay control circuit voltage does not match the commanded state of the ODM. DTC P0685 sets when an open, high resistance, short to ground, or a short to battery positive voltage is detected on the powertrain relay coil control circuit.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0685 Engine Controls Ignition Relay Control Circuit
Conditions for Running the DTC
| • | The battery voltage is between 9-16 volts. |
| • | The ignition switch is turned ON. |
| • | The powertrain relay has been commanded ON. |
Conditions for Setting the DTC
| • | The commanded state of the ODM and the actual state of the control circuit do not match. |
| • | The condition is present for more than 5 seconds. |
Action Taken When the DTC Sets
| • | The control module stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in Failure Records. |
| • | The driver information center, if equipped, may display a message. |
Conditions for Clearing the MIL/DTC
| • | A current DTC, last test failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears 40 consecutive warm-up cycles, if this or any other related diagnostic reports no other failures. |
| • | Clear the DTC with a scan tool. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Electrical Center Identification Views , Engine Control Module Connector End Views , and Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Did the DTC fail this ignition? | -- | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections |
3 |
Notice: Refer to Test Probe Notice in the Preface section. Does the test lamp illuminate? | -- | Go to Step 12 | Go to Step 4 |
4 |
Does the test lamp illuminate? | -- | Go to Step 5 | Go to Step 11 |
5 |
Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 6 |
6 |
Does the test lamp illuminate? | -- | Go to Step 14 | Go to Step 9 |
7 |
Notice: Refer to Test Probe Notice in the Preface section. Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 17 |
8 |
Does the test lamp illuminate? | -- | Go to Step 19 | Go to Step 18 |
9 |
Does the resistance measure more than the specified value? | 3 ohms | Go to Step 20 | Go to Step 10 |
10 | 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 . Does the resistance measure more than the specified value? | 3 ohms | Go to Step 18 | Go to Step 17 |
11 | 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 test lamp illuminate? | -- | Go to Step 18 | |
12 |
Does the test lamp illuminate? | -- | Go to Step 13 | Go to Step 17 |
13 |
Does the test lamp illuminate? | -- | Go to Step 21 | Go to Step 23 |
14 | Measure the resistance from terminal #85 of the powertrain relay to terminal #86 with a DMM. Refer to Troubleshooting with a Digital Multimeter . Does the resistance measure within the specified value? | 70-110 ohms | Go to Step 15 | Go to Step 22 |
15 | Measure the resistance from terminal #30 of the powertrain relay to terminal #86 with a DMM. Refer to Troubleshooting with a Digital Multimeter . Does the DMM display OL? | -- | Go to Step 16 | Go to Step 22 |
16 | Test for an intermittent and for a poor connection at the powertrain relay terminals on the underhood fuse block. Refer to Testing for Intermittent Conditions and Poor Connections . Did you find a condition? | -- | Go to Step 23 | Go to Testing for Intermittent Conditions and Poor Connections |
17 | Test for shorted terminals and poor connections at the ECM electrical connector, and at the ECM wire harness electrical connector. Refer to Testing for Intermittent Conditions and Poor Connections . Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 24 |
18 | Test for shorted terminals and poor connections at the underhood fuse block electrical connector, and at the underhood fuse block wire harness electrical connector. Refer to Testing for Intermittent Conditions and Poor Connections . Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 23 |
19 | Repair the short to ground in the powertrain relay coil control circuit, between the underhood fuse block wire harness electrical connector and the ECM wire harness electrical connector. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 25 | -- |
20 | Repair the high resistance or the open in the powertrain relay coil control circuit, between the underhood fuse block wire harness electrical connector and the ECM wire harness electrical connector. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 25 | -- |
21 | Repair the short to battery positive voltage in the powertrain relay coil control circuit, between the underhood fuse block wire harness electrical connector and the ECM wire harness electrical connector. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 25 | -- |
22 | Replace the powertrain relay. Refer to Relay Replacement . Did you complete the replacement? | -- | Go to Step 25 | -- |
23 | Replace the underhood fuse block. Refer to Underhood Electrical Center or Junction Block Replacement . Did you complete the replacement? | -- | Go to Step 25 | -- |
24 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 25 | -- |
25 |
Did the DTC fail this ignition? | -- | Go to Step 3 | Go to Step 26 |
26 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
