P0685
DTC P0685
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptor
DTC P0685
- Engine Controls Ignition Relay Control Circuit
Diagnostic Fault Information
Circuit/System Description
The powertrain relay is a normally open relay. The relay switch is held in the open position by spring tension. Battery positive voltage is supplied directly to the relay coil and the relay switch contact at all times. The powertrain control module (PCM) supplies the ground path to the relay coil control circuit through an output driver module (ODM). The ODM for the powertrain relay also incorporates a fault detection circuit, which is continuously monitored by the PCM. When the PCM commands the powertrain relay ON, ignition 1 voltage is supplied to the following fuses in the underhood fuse block:
* ETC fuse
* Emissions fuse
* ELEK Ign fuse
* Fuel Inj fuse
* O2 SSR fuse
The ignition 1 voltage that is supplied to the PCM through the ETC fuse, provides power to the internal PCM circuits associated with the throttle actuator control (TAC) operation. The PCM also monitors the voltage level on the ignition 1 voltage circuit to confirm that the powertrain relay contacts have closed.
Conditions for Running the DTC
* The battery voltage is between 9-18 volts.
* The ignition is ON.
* The powertrain relay has been commanded ON.
Conditions for Setting the DTC
* The commanded state of the ODM does not match and the actual state of the control circuit.
* The condition is present for more than 5 seconds.
Action Taken When the DTC Sets
DTC P0685 is a Type B DTC.
Conditions for Clearing the MIL/DTC
DTC P0685 is a Type B DTC.
Diagnostic Aids
* This test procedure assumes that the vehicle battery has passed a load test and is completely charged. Refer to Battery Inspection/Test (Battery Inspection/Test).
* When disconnecting electrical connectors or removing fuses and relays from a fuse block, always inspect the component electrical terminals for corrosion and the mating electrical terminals for correct tension.
Reference Information
Schematic Reference
Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Powertrain Control Module Description (Powertrain Control Module Description)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. With the ignition ON, engine OFF, command the powertrain relay ON and OFF several times using the scan tool output control function. You should either hear or feel the relay click with each command.
2. With the ignition ON, engine OFF, probe both test points of each of the following fuses:
3. ETC fuse
4. Emissions fuse
5. ELEK Ign fuse
6. Fuel Inj fuse
7. O2 SSR fuse
8. Ignition OFF, observe the Ignition 1 voltage parameter. The parameter should be 0 volt before the PCM powers down.
Circuit/System Testing
1. With the ignition OFF, remove the powertrain relay from the underhood fuse block.
2. With the ignition ON, measure for battery positive voltage, B+, between the relay coil voltage supply circuit and ground.
• If the voltage measures less than B+, repair the open or high resistance in the circuit to the relay coil. All wire circuit resistance should measure less than 2 ohms.
3. Measure for voltage between the relay coil control circuit and ground.
• If voltage is measured on the control circuit of the relay, test for a short to voltage.
4. Connect a test lamp between the battery positive voltage supply circuit of the relay coil and the relay coil control circuit. Use a scan tool to command the powertrain relay ON and OFF. The test lamp should turn ON and OFF when toggling between the commanded states.
• If the test lamp stays ON all the time, test for a short to ground on the relay coil control circuit. If the circuits test normal, replace the control module.
• If the test lamp stays OFF all the time, test for an open or high resistance on the relay coil control circuit. If the circuits test normal, replace the control module. All wire circuit resistance should measure less than 2 ohms.
5. Measure for B+ between the relay armature supply circuit, and ground.
• If the voltage measures less than B+, repair the open or high resistance in the circuit to the relay armature. All wire circuit resistance should measure less than 2 ohms.
Important: A short to battery voltage on any control circuit may keep the PCM powered up.
6. Ignition OFF, ensure the PCM is powered down. Measure for battery voltage between the relay armature supply circuit and ground. There should be no voltage present.
• If voltage is present, test each control circuit for the components which are supplied by the powertrain relay for a short to B+.
7. With the ignition ON, test for voltage on each test point of the ETC fuse.
• If voltage is present, test the ignition 1 voltage circuit between the PCM, the powertrain relay, and the ETC fuse for a short to voltage.
• If both circuits test normal, replace the PCM.
8. Connect a 20A fused jumper wire between the B+ terminal and the ignition 1 voltage terminal of the powertrain relay at the underhood fuse block. With a test lamp, probe both test points of the ETC fuse.
• If the test lamp illuminates at both test points of the ETC fuse, repair the ignition 1 voltage circuit between the powertrain relay and the PCM for an open or high resistance. If the circuits test normal, replace the control module. All wire circuit resistance should measure less than 2 ohms.
• If the test lamp only illuminates at one test point of the ETC fuse, repair the short to ground in the ignition 1 voltage circuit between the fuse and the applicable component. Replace the fuse, as necessary.
• If the test lamp does not illuminate on either test point of the ETC fuse, repair the open or high resistance between the powertrain relay and the ETC fuse. All wire circuit resistance should measure 2 ohms or less.
9. With a test lamp, test for voltage on both test points of the following fuses:
10. ETC fuse
11. Emissions fuse
12. ELEK Ign fuse
13. Fuel Inj fuse
14. O2 SSR fuse
• If the test lamp fails to illuminate on one test point of each fuse, repair the open or high resistance between the fuse and the powertrain relay. All wire circuit resistance should measure 2 ohms or less.
15. If all circuits test normal, test or replace the relay.
Component Testing
* Measure for 70-110 ohms between terminals 85 and 86 of the relay.
• If the resistance is not within the specified range, replace the relay.
* Measure for infinite resistance between terminals 30 and 86 of the relay.
• If continuity is detected, replace the relay.
* Measure for infinite resistance between terminals 30 and 87 of the relay.
• If continuity is detected, replace the relay.
* Measure for infinite resistance between terminals 30 and 85 of the relay.
• If continuity is detected, replace the relay.
* Measure for infinite resistance between terminals 85 and 87 of the relay.
• If continuity is detected, replace the relay.
* Connect a 20A fused jumper wire from the battery positive cable at the battery, to relay terminal 85. Connect a jumper wire from the negative battery cable at the battery, to relay terminal 86. Measure for less than 2 ohms between terminals 30 and 87 of the relay, with a DMM.
• If the resistance measures more than 2 ohms, replace the relay.
Repair Instructions
* Control Module References (Programming and Relearning) for PCM replacement, setup, and programming
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
Repair Verification
1. Clear the DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine. If engine does not run, refer to Engine Cranks but Does Not Run (Engine Cranks But Does Not Run).
4. If other DTCs are set, refer to Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview).