Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptors
DTC P0685: Engine Controls Ignition Relay Control CircuitDTC P0690: Engine Controls Relay Feedback Circuit High Voltage
Diagnostic Fault Information
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
Battery Supply Voltage-Coil | P1516, P1682 | P0685 | P1516, P1682 | -- | -- |
Battery Supply Voltage-Armature | -- | P1516, P1682 | P1516, P1682 | -- | -- |
Ign 1 Relay Control Circuit | P0690 | P0685 | P1516, P1682 | P0685, P1516, P1682, P2176 | -- |
Ignition 1 Voltage Circuit | -- | P1516, P1682 | P1516, P1682 | -- | -- |
Typical Scan Tool Data
Display Parameters | Normal Range | Short to Ground | Open | Short to Voltage |
|---|---|---|---|---|
Operating Conditions: Ignition ON with the engine OFF | ||||
Battery Supply Voltage-Coil | -- | 0 V | 0 V | -- |
Battery Supply Voltage-Armature | -- | 0 V | 0 V | -- |
EC Ignition Relay Control | -- | 0 V | 0 V | -- |
EC Ignition Relay Feedback | 11.9-12.9 V | 0 V | 0 V | More than 2 V* |
*DTC P0690 will set if the ECM detects voltage when the ignition is in the OFF position. | ||||
Circuit/System 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). The 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 powertrain relay ON, ignition 1 voltage is supplied to the ECM, and to several additional circuits.
Conditions for Running the DTC
P0685
| • | The ignition is ON. |
| • | The battery voltage is between 9-16 volts. |
P0690
| • | This DTC will run with the ignition ON or OFF. |
| • | This DTC will run when the powertrain relay is commanded ON or OFF. |
| • | DTC P0685 is not set. |
Conditions for Setting the DTC
P0685
| • | 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. |
P0690
| • | The ECM detects more than 16 volts on the ignition 1 voltage circuit to the ECM when the relay is commanded ON. |
| • | The ECM detects more than 2 volts on the ignition 1 voltage circuit to the ECM when the relay is commanded OFF. |
| • | The condition is present for more than 2 seconds. |
Action Taken When the DTC Sets
DTCs P0685 and P0690 are Type B DTCs.
Conditions for Clearing the DTC
DTCs P0685 and P0690 are Type B DTCs.
Diagnostic Aids
This test procedure requires that the vehicle battery has passed a load test and is completely charged. Refer to Battery Inspection/Test.
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Special Tools
| • | J 35616 GM-Approved Terminal Test Kit |
| • | J 43244 Relay Puller Pliers |
Circuit/System Verification
- Engine running, command the powertrain relay ON and OFF, with a scan tool, while observing the following powertrain relay coil control circuit status parameters.
- Ignition ON, engine OFF, with a test lamp, probe both test points of all the fuses that are powered by the powertrain relay. The test lamp should illuminate ON for at least one test point of each fuse.
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
| • | EC Ign. Relay Ckt. Short Gnd Test Status |
| • | EC Ign. Relay Ckt. Open Test Status |
| • | EC Ign. Relay Ckt. Short Volts Test Status |
| • | Each parameter should toggle between OK and Not Run. |
Circuit/System Testing
- Ignition OFF, disconnect the Ign 1 relay.
- Ignition ON, verify that a test lamp illuminates between the Ign 1 relay coil B+, and ground.
- Ignition OFF, verify that a test lamp does not illuminate between the Ign 1 relay coil B+ circuit and the control circuit.
- Remove the test lamp.
- Command the engine control ignition relay ON, with a scan tool. Verify with a scan tool that the EC Ign 1 Relay Ckt. Short Volts Test Status parameter is OK.
- Test the coil side of the Ign 1 relay for 65-110 ohms.
- Ignition OFF, disconnect the ECM X1 connector.
- Test the Ign 1 relay control circuit for an open/high resistance.
- Verify that a test lamp does not illuminate between the relay ignition 1 voltage circuit and ground.
- Verify that a test lamp illuminates between the relay switch B+ and ground.
- Connect a 20 A fused jumper wire between the relay switch B+ and the relay ignition 1 voltage circuit.
- Ignition ON, engine OFF, monitor the EC Ignition Relay Feedback parameter with a scan tool. The parameter should display B+.
- If all circuits test normal, replace the relay.
Important: You must perform the Circuit/System Verification first.
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the battery positive cable to the underhood fuse block. |
| ⇒ | If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM. |
| ⇒ | If not the specified value, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
| ⇒ | If not within the specified value, replace the relay. |
| ⇒ | If the circuit tests normal, replace the ECM. |
| ⇒ | If the test lamp illuminates, test the relay ignition 1 voltage circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
| ⇒ | If the test lamp does not illuminate, test the relay switch B+ circuit for a short to ground, or an open/high resistance. If the circuits test normal, and the fuse for the ignition 1 voltage circuit is open, test the ignition 1 voltage circuit to the ECM for a short to ground. If the circuit tests normal, replace the ECM. |
| ⇒ | If the parameter does not display B+, test the ignition 1 voltage circuit for an open/high resistance. If the circuit tests normal, replace the ECM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for ECM replacement, setup, and programming
