DTC P0703: Brake Switch Sense Circuit: Testing
- Turn ignition on. Using scan tool, read DTCs. If GOOD TRIP counter is displayed and equal to zero, go to next step. If GOOD TRIP counter is not displayed and equal to zero, go to step 9
.NOTE: Power for brake switch sense circuit comes from Brake Transmission Shift Interlock (BTSI) solenoid, and fuse No. 14 (10-amp) in junction block.
- Turn ignition off. Disconnect brakelight switch harness connector located above brake pedal. Connect a test light between ground and brake switch sense circuit (White/Pink wire) at brakelight switch harness connector terminal No. 1. See Fig 1 . If test light illuminates brightly, go to next step. If test light does not illuminate brightly, repair open or short in fused ignition switch output circuit between brakelight switch and BTSI solenoid. BTSI solenoid is located on steering column.
- Disconnect PCM harness connectors. See Figure . Remove Auto Shutdown (ASD) relay from Power Distribution Center (PDC). See Figure . Connect a jumper wire between fused battery voltage circuit (Red/White wire) at terminal "B" and ASD relay output circuit (Dark Green/Orange wire) at terminal "D" at ASD relay harness connector. Turn ignition on. Measure voltage between ground and brake switch sense circuit (White/Pink wire) at brakelight switch harness connector terminal No. 1. If voltage is one volt or less, go to next step. If voltage is more than one volt, repair short to voltage in White/Pink wire.
- Turn ignition off. Remove jumper wire. Measure resistance between ground and brake switch sense circuit (White/Pink wire) at brakelight switch harness connector terminal No. 1. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short to ground in White/Pink wire.
- Measure resistance of brake switch sense circuit (White/Pink wire) between brakelight switch harness connector terminal No. 1 and terminal No. 62 at PCM C2 harness connector. See Figure . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in White/Pink wire.
- Measure resistance of ground circuit (Black/Light Green wire) between terminal No. 2 at brakelight switch harness connector and ground located under center of instrument panel. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in ground circuit.
- Measure resistance between brakelight switch terminals No. 1 and 2 (component side). With brake pedal released, resistance should be less than 5 ohms. With brake pedal applied, resistance should be 5 ohms or more. If resistance is as specified, go to next step. If resistance is not as specified, replace brakelight switch.
- If no other possible causes are remaining, replace PCM.
- Conditions that set DTC are not present at this time. Perform the following to help identify intermittent condition:
- With engine running at normal operating temperature, wiggle related wiring harness while monitoring related parameters on scan tool. If voltage changes or DTC sets while wiggling wiring harness, repair connectors or wiring harness where wiggling caused voltage to change or DTC to set.
- Review freeze frame information on scan tool. Duplicate conditions present when DTC was set.
- Refer to any technical service bulletins that may apply.
- Visually inspect related wiring harness. Check for chafed, pierced, pinched or partially broken wires.
- Visually inspect related wiring harness connectors. Check for broken, bent, pushed out or corroded terminals.
If a problem is found, repair as necessary. If no problems are found, test is complete.