DTC B1440: Power Mode Master Input Circuits Mismatch
Class 2 communications will not start until vehicle systems "on" power mode has been identified. Three discrete wires from ignition switch contacts are monitored by Instrument Panel Cluster (IPC) in order to determine the present power mode (ignition switch position). IPC communicates system power mode to all modules on the class 2 data line.
When the fault is detected IPC is powered and one of the monitored ignition switch circuits has malfunctioned. IPC will implement default values for ignition switch input parameters when faulty ignition switch circuits are detected.
- Turn ignition switch to ON position. Perform instrument cluster diagnostic system check. See INSTRUMENT CLUSTER DIAGNOSTIC SYSTEM CHECK . Go to next step.
- Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. Using scan tool, select IP input data list. Select ignition switch input parameters. Check for smooth ignition switch operation and smooth changes of input values between ACTIVE and INACTIVE on scan tool. With ignition switch in ON position, or in ON position with engine running, all ignition switch input parameter values should be displayed as ACTIVE on scan tool. If any ignition input parameter values display INACTIVE, go to next step. If all ignition switch parameter values displayed read ACTIVE, go to step 6 .
- Test any ignition switch circuits that display INACTIVE on scan tool for an open or short to ground. See WIRING DIAGRAMS . Repair any open or shorted wiring conditions found and go to step 12 . If wiring and connections are okay, go to next step.
- Check for intermittent or poor connections at Instrument Panel Cluster (IPC) connectors C1 and C2. See Fig 1 . Repair wiring or connectors as necessary. If wiring and connectors are okay, go to next step.
- Check for intermittent or poor connections at ignition switch. Repair wiring or connectors as necessary. If wiring and connectors are okay, go to next step.
- Turn ignition switch to OFF position. Using scan tool, observe ignition switch input parameters. If scan tool can communicate and ignition input parameter for ignition 1 circuit (IGN1) reads as ACTIVE, go to step 8 . If scan tool does not communicate with scan tool or does not display ignition 1 parameter (IGN1) as ACTIVE, go to next step.
- Turn ignition switch to ACC position. Using a test light connected to ground, backprobe IGN1 and IGN0 circuits at ignition switch. Test light should not illuminate. If test light does not illuminate, go to step 11 . If test light illuminated at either terminal, go to step 10 .
- Test ignition switch circuits that displayed ACTIVE in step 6 for a short to voltage. If short to voltage is found, repair wiring as necessary and go to step 12 . If short to voltage was not found, go to next step.
- Turn ignition switch to ACC position. Using a test light connected to ground, backprobe ACTIVE circuits from step 6 . If test light illuminates for either circuit, go to next step. If test light did not illuminate, go to step 11 .
- Replace ignition switch. See appropriate STEERING COLUMN SWITCHES article. After repairs, go to step 12 .
- Replace instrument cluster. See INSTRUMENT CLUSTER under REMOVAL & INSTALLATION. Contact an authorized A/C Delco service center for transfer of information from failed Instrument Panel Cluster (IPC) or affix appropriate label with necessary vehicle information on driver door pillar. After repairs, go to next step.
- Operate system to verify normal operation. Perform instrument cluster diagnostic system check. See INSTRUMENT CLUSTER DIAGNOSTIC SYSTEM CHECK . If fault remains, go to step 2 .