2010 Cadillac CTS Sedan AWD V6-3.6L Page 1584
5. Ignition ON, observe the scan tool EC Ignition Relay Feedback Signal parameter. The ECM should communicate, and the parameter should
display 9-14 V.
瀚慖f not the specified range, or the ECM does not communicate, test the ignition voltage circuit between the powertrain relay and the ECM
for a short to ground or for an open/high resistance. If the circuit/connections test normal, replace the K20 ECM.
6. Ignition OFF, verify that a test lamp does not illuminate between the control circuit terminal 86 and B+.
瀚慖f the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the K20 ECM.
7. Connect a DMM set to the diode setting between the control circuit terminal 86 and ground.
8. Ignition ON, verify the DMM does not display OL.
瀚慖f the DMM displays OL, test the control circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the
K20 ECM.
9. If all circuits test normal, replace the KR75 powertrain relay.
Component Testing
Note: Depending on the application, the relay coil resistance will be within one of the following ranges.
1. Test for one of the following resistance specifications between terminals 85 and 86 of the KR75 powertrain relay:
* 70-110 ohm
* 200-250 ohm
瀚慖f not within the specified range, replace the KR75 powertrain relay.
2. Measure for infinite resistance between the following terminals of the KR75 powertrain relay:
* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
瀚慖f continuity is detected, replace the KR75 powertrain relay.
3. Connect a 20 A fused jumper wire from the positive terminal of the battery to relay terminal 85. Connect a jumper wire from the negative
terminal of the battery to relay terminal 86. Measure for less than 2 Ohms between terminals 30 and 87 of the relay.
瀚慖f greater than the specified value, replace the KR75 powertrain relay.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) (See: Power and Ground Distribution/Power Distribution Relay/Service and Repair/Relay
Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (See: Power and Ground Distribution/Power
Distribution Relay/Service and Repair/Relay Replacement (Within an Electrical Center))
* Control Module References (See: Testing and Inspection/Programming and Relearning) for engine control module replacement, setup, and
programming
P0686
DTC P0685, P0686, P0687, P0689, or P0690
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC P0685
- Engine Controls Ignition Relay Control Circuit
