For a complete wiring diagram Refer to Section 8WWhen Monitored:With the ignition on.Set Condition:The Engine Control Module (ECM) detects that the (T26) Clutch Upstop Switch Signal circuit signal is implausible.Possible CausesINTERMITTENT DTC(T26) CLUTCH UPSTOP SWITCH SIGNAL CIRCUIT SHORTED TO VOLTAGE(T26) CLUTCH UPSTOP SWITCH SIGNAL CIRCUIT SHORTED TO GROUND(T26) CLUTCH UPSTOP SWITCH SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE(Z905) GROUND CIRCUIT OPEN OR HIGH RESISTANCECLUTCH INTERLOCK SWITCHENGINE CONTROL MODULE (ECM)Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)1. DTC IS ACTIVEIgnition on, engine not running.With the scan tool, Clear DTCs in the Engine Control Module (ECM).Press and release the clutch pedal several times.With the scan tool, select View DTCs.Is the status Active for this DTC?YesGo To 2 NoRefer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure.(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)2. (T26) CLUTCH UPSTOP SWITCH SIGNAL CIRCUIT VOLTAGE

Turn the ignition off.Disconnect the Clutch Interlock Switch harness connector.Turn the ignition on.Measure the voltage of the (T26) Clutch Upstop Switch Signal circuit in the Clutch Interlock Switch harness connector.Is the voltage above 10.0 volts?YesGo to 3NoGo to 53. (Z905) GROUND CIRCUIT OPEN OR HIGH RESISTANCE

Using a 12 volt test light connected to 12 volts, check the (Z905) Ground circuit between the Clutch Interlock Switch harness connector.The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.Is the test light illuminated and bright?YesGo to 4NoRepair the (Z905) Ground for an open circuit or high resistance.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)4. CLUTCH INTERLOCK SWITCHTurn the ignition off.Connect a jumper wire between the (Z905) Ground circuit and the (T26) Clutch Upstop Switch Signal circuit in the Clutch Interlock Switch harness connector.Turn the ignition on.With the scan tool, monitor the Clutch Upstop status.The scan tool should display the Clutch Interlock status as not pressed with the jumper wire in place and pressed with the jumper wire removed.Does the scan tool display the status as described above?YesReplace the Clutch Interlock Switch in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo to 85. (T26) CLUTCH UPSTOP SWITCH SIGNAL CIRCUIT SHORTED TO VOLTAGE

Turn the ignition off.Disconnect the Engine Control Module (ECM) harness connector.Remove the ASD Relay from the TIPM.Connect a jumper wire between cavity 30 and cavity 87 of the ASD Relay connector.Turn the ignition on.Measure the voltage of the (T26) Clutch Upstop Switch Signal circuit in the Clutch Interlock Switch harness connector.Is there any voltage present?YesRepair the (T26) Clutch Upstop Switch Signal circuit for a short to voltage.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo to 66. (T26) CLUTCH UPSTOP SWITCH SIGNAL CIRCUIT SHORTED TO GROUND

Turn the ignition off.Measure the resistance between ground and the (T26) Clutch Upstop Switch Signal circuit in the Clutch Interlock Switch harness connector.Is the resistance above 1000 ohms?YesGo to 7NoRepair the (T26) Clutch Upstop Switch Signal circuit for a short to ground.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)7. (T26) CLUTCH UPSTOP SWITCH SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE

Measure the resistance of the (T26) Clutch Upstop Switch Signal circuit between the Clutch Interlock Switch harness connector and the Engine Control Module (ECM) harness connector.Is the resistance below 10.0 ohms?YesGo to 8NoRepair the (T26) Clutch Upstop Switch Signal circuit for an open circuit or high resistance.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)8. ENGINE CONTROL MODULE (ECM)Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Clutch Interlock Switch and the Engine Control Module (ECM).Look for any chafed, pierced, pinched, or partially broken wires.Look for broken, bent, pushed out or corroded terminals.Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.Look for the data to change or for the DTC to reset during the wiggle test.Refer to any Technical Service Bulletins that may apply.Were any problems found?YesRepair as necessary.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoReplace the Engine Control Module (ECM) in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)