Diagnostic Procedure
- Perform ON-BOARD DIAGNOSTIC II SYSTEM CHECK
under SELF-DIAGNOSTIC SYSTEM. After performing OBD-II system check, go to next step.
- Observe speedometer while test driving vehicle. If speedometer works, go to step 10
. If speedometer does not work, go to next step.
- Turn ignition off. Disconnect Vehicle Speed Sensor (VSS) 3-pin harness connector. VSS is located in transmission tail shaft housing. Turn ignition on. Using test light connected to battery voltage, probe VSS harness connector terminal No. 2 (Black wire). See Fig 1
. If test light illuminates, leave harness connector disconnected and go to step 5
. If test light does not illuminate, go to next step.
- Repair open in Black wire (VSS ground) between ground point E-23 and VSS. See ENGINE PERFORMANCE
in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Ground point is located at right rear corner of engine compartment, on fender well. After repair is complete, see VERIFYING VEHICLE REPAIR
under SELF-DIAGNOSTIC SYSTEM.
- Turn ignition on. Using DVOM, measure voltage between VSS harness connector terminals No. 1 (Red/Green wire) and No. 2 (Black wire). See Fig 1
. If battery voltage exists, leave harness connector disconnected and go to step 7
. If battery voltage does not exist, go to next step.
- Repair open or short to ground in Red/Green wire (ignition voltage) between ECM and VSS. See ENGINE PERFORMANCE
in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. After repair ensure fuse is not blown. After repair is complete, see VERIFYING VEHICLE REPAIR
under SELF-DIAGNOSTIC SYSTEM.
- Turn ignition on. Using DVOM, measure voltage between ground and VSS harness connector terminal and No. 3 (Black/Yellow wire). Voltage reading should be 7.5-8.0 volts. If voltage is as specified, go to step 9
. If voltage is not as specified, go to next step.
- Check for and repair open or short in Black/Yellow wire between speedometer and VSS. See ENGINE PERFORMANCE
in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. After repair is complete, see VERIFYING VEHICLE REPAIR
under SELF-DIAGNOSTIC SYSTEM.
- Replace speedometer. See appropriate INSTRUMENT PANELS - article in ACCESSORIES & EQUIPMENT. After repair is complete, see VERIFYING VEHICLE REPAIR
under SELF-DIAGNOSTIC SYSTEM.
- Turn ignition off. Disconnect MAF sensor 3-pin harness connector, (the connector attaches the VSS wires from the transmission harness to the left side engine harness). MAF sensor is located in air intake pipe, at air cleaner housing. Remove air cleaner assembly. Disconnect Black 16-pin in-line harness connector. Harness connector is located on left inner fender panel behind air cleaner housing. Connect fused jumper wire between battery voltage and Blue/Yellow wire on transmission side of in-line harness connector. See Fig 2
. See ENGINE PERFORMANCE
in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Connect positive side of DVOM to Light Green/White wire, (next to the Blue/Yellow wire) on transmission side of in-line harness connector. Disconnect the Blue connector next to the Black 16-pin in-line harness connector. Locate the Black/Red wire at one corner of the Blue connector. This wire is VSS ground. With a jumper wire connect Black/Red wire at one corner of the Blue connector to ground. Connect negative side of DVOM to ground. Raise and support rear of vehicle. Place transmission in Neutral. Turn ignition on. Observe DVOM readings, while rotating rear wheels by hand. Voltage reading should toggle back and forth between 0.6-10 volts. If voltage toggles as specified, go to step next step. If voltage does not toggle as specified, go to step 12
.
- Replace VSS. See REMOVAL & INSTALLATION
article. After repair is complete, see VERIFYING VEHICLE REPAIR
under SELF-DIAGNOSTIC SYSTEM.
- Check for and repair open or short between ECM and speedometer harness connector. See ENGINE PERFORMANCE
in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. After repair is complete, see VERIFYING VEHICLE REPAIR
under SELF-DIAGNOSTIC SYSTEM. If no problem with wiring is found, go to next step.
- Replace and reprogram ECM. See POWERTRAIN CONTROL MODULE REPLACEMENT
under POWERTRAIN CONTROL MODULE. Use scan tool to clear DTC and verify repair.
Courtesy of ISUZU MOTOR CO.
Courtesy of ISUZU MOTOR CO.