Bus +/- Signals Open Or No Response From Compass Mini-Trip Computer

Possible Causes:

Ground Circuit Open
Fused Ignition Switch Output Circuit Open
Fused B+ Circuit Open
Open PCI Bus Circuit
Compass Mini-Trip Computer

Testing

NOTE: Ensure there is PCI Bus Communication with other modules on the vehicle before proceeding. If not, diagnose and repair Communication problem as necessary. See COMMUNICATIONS in DIAGNOSTIC TROUBLE CODE IDENTIFICATION and SYMPTOM IDENTIFICATION tables.

Turn the ignition off. Disconnect the Compass Mini-Trip Computer harness connector. Using a 12-volt test light connected to 12-volts, probe the ground circuit. Is the test light illuminated? If yes, go to next step. If no, repair the ground circuit for an open. Perform BODY VERIFICATION TEST .
Turn the ignition off. Disconnect the Compass Mini-Trip Computer harness connector. Turn the ignition on. Using a 12-volt test light connected to ground, probe the Fused Ignition Switch Output circuit. Is the test light illuminated? If yes, go to next step. If no, repair the Fused Ignition Switch Output circuit for an open. See WIRING DIAGRAMS . Perform BODY VERIFICATION TEST .
Turn the ignition off. Disconnect the Compass Mini-Trip Computer harness connector. Using a 12-volt test light connected to ground, probe the Fused B+ circuit. Is the test light illuminated? If yes, go to next step. If no, repair the Fused B+ circuit for an open. See WIRING DIAGRAMS . Perform BODY VERIFICATION TEST .
Disconnect the Compass Mini-Trip Computer harness connector. Use Scope Input Cable (CH7058), Cable-to-Probe adapter (CH7062), and the red and black rest probes. Connect the scope input cable to the channel one connector on the DRBIII(R). Attach the red and black leads and the cable to probe adapter to the scope input cable. With the DRBIII(R) select Pep Module Tools. Select lab scope. Select Live Data. Select 12-volt square wave. Press F2 for Scope. Press F2 and use the down arrow to set voltage range to 20 volts. Set Probe to x10. Press F2 again when complete. Connect the Black lead to the chassis ground. Connect the Red lead to the PCI Bus circuit in the Compass Mini-Trip Computer connector. Turn the ignition on. Observe the voltage display on the DRBIII(R) Lab Scope. Does the voltage pulse from 0 to approximately 7.5 ohms? If yes, replace the Compass Mini-Trip Computer in accordance with the service information. Perform BODY VERIFICATION TEST . If no, repair the PCI Bus circuit for an open. Perform BODY VERIFICATION TEST .