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2008 - MX-5 - Engine

DTC P0703 [LF]



DTC P0703

Brake switch input circuit problem

DETECTION CONDITION

  • The PCM monitors changes in input voltage from the brake switch No.1. If the PCM does not the voltage changes while alternately accelerating and decelerating 8 times, the PCM determines that the brake switch No.1 circuit has a malfunction.

    Diagnostic support note
  • This is a continuous monitor (CCM).

  • The MIL illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.

  • PENDING CODE is available if the PCM detects the above malfunction condition during the first drive cycle.

  • FREEZE FRAME DATA is available.

  • The DTC is stored in the PCM memory.

POSSIBLE CAUSE

  • Brake switch malfunction

  • Poor connection of brake switch connector or PCM connector

  • Short to power supply in wiring harness between brake switch No.1 terminal D and PCM connector terminal 1AB

  • Open circuit in wiring harness between brake switch No.1 terminal D and PCM connector terminal 1AB

  • Open circuit in wiring harness between battery positive terminal and brake switch No.1 terminal B

  • PCM malfunction


Diagnostic procedure

STEP

INSPECTION

ACTION

1

VERIFY FREEZE FRAME DATA HAS BEEN RECORDED
  • Has FREEZE FRAME DATA been recorded?

Yes

Go to the next step.

No

Record the FREEZE FRAME DATA on the repair order, then go to the next step.

2

VERIFY RELATED REPAIR INFORMATION AVAILABILITY
  • Verify related Service Bulletins and/or on-line repair information availability.

  • Is any related repair information available?

Yes

Perform repair or diagnosis according to the available repair information.

  • If the vehicle is not repaired, go to the next step.

No

Go to the next step.

3

CLASSIFY HIGH INPUT OR LOW INPUT
  • Connect the M-MDS to DLC‐2.

  • Access BOO PID.

  • Verify BOO PID during brake pedal operation.

  • Is BOO PID always OFF?

Yes

Go to the next step.

No

Go to Step 10.

4

INSPECT BRAKE SWITCH CONNECTOR FOR POOR CONNECTION
  • Turn the ignition switch off.

  • Disconnect the brake switch connector.

  • Inspect for poor connection (such as damaged/pulled-out pins, corrosion).

  • Is there any malfunction?

Yes

Repair or replace the terminal, then go to Step 13.

No

Go to the next step.

5

CLASSIFY BRAKE SWITCH OR CIRCUIT
  • Connect the M-MDS to DLC‐2.

  • Access BOO PID.

  • Connect a jumper wire between brake switch No.1 terminal B and D.

  • Is BOO PID on?

Yes

Go to the next step.

No

Go to Step 7.

6

INSPECT BRAKE SWITCH

Yes

Go to Step 13.

No

Replace the brake switch, then go to Step 13.

(See BRAKE PEDAL REMOVAL/INSTALLATION.)

7

INSPECT BRAKE SWITCH POWER CIRCUIT FOR OPEN CIRCUIT
  • Measure the voltage between brake switch terminal B and body ground.

  • Is the voltage B+?

Yes

Go to the next step.

No

Repair or replace the brake switch power circuit for open, then go to Step 13.

8

INSPECT PCM CONNECTOR FOR POOR CONNECTION
  • Turn the ignition switch off.

  • Disconnect the PCM connector.

  • Inspect for poor connection (such as damaged/pulled-out pins, corrosion).

  • Is there any malfunction?

Yes

Repair or replace the terminal, then go to Step 13.

No

Go to the next step.

9

INSPECT BRAKE SWITCH SIGNAL CIRCUIT FOR OPEN CIRCUIT
  • Inspect for continuity between brake switch terminal D and PCM terminal 1AB.

  • Is there continuity?

Yes

Go to Step 13.

No

Repair or replace the wiring harness for an open circuit, then go to Step 13.

10

CLASSIFY BRAKE SWITCH OR CIRCUIT
  • Connect the M-MDS to DLC‐2.

  • Access BOO PID.

  • Verify that BOO PID changes from ON to OFF when the brake switch connector disconnected.

  • Does BOO PID change from ON to OFF?

Yes

Go to the next step.

No

Go to Step 12.

11

INSPECT BRAKE SWITCH

Yes

Go to Step 13.

No

Replace the brake switch, then go to Step 13.

(See BRAKE PEDAL REMOVAL/INSTALLATION.)

12

INSPECT BRAKE SWITCH SIGNAL CIRCUIT FOR SHORT TO POWER SUPPLY
  • Measure the voltage between brake switch terminal D and body ground.

  • Is the voltage B+?

Yes

Repair or replace the wiring harness for short to power supply, then go to the next step.

No

Go to the next step.

13

VERIFY TROUBLESHOOTING OF DTC P0703 COMPLETED
  • Make sure to reconnect all disconnected connectors.

  • Clear the DTC from the PCM memory using the M-MDS.

  • Drive the vehicle 30 km/h {18.6 mph} or more.

  • Depress and release the brake pedal more than 8 times while driving vehicle.

  • Is the PENDING CODE for this DTC present?

Yes

Replace the PCM, then go to the next step.

(See PCM REMOVAL/INSTALLATION [LF].)

No

Go to the next step.

14

VERIFY AFTER REPAIR PROCEDURE

Yes

Go to the applicable DTC troubleshooting.

(See DTC TABLE [LF].)

No

Troubleshooting completed.




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