DTC 138: Brake Pedal Position Switch Malfunction

WARNING: This page is about a different car, the 2013 Acura MDX, 2012 Acura MDX, 2011 Acura MDX, and 2010 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).

Turn the ignition switch to ON (II).
Check for DTCs with the HDS.
Is DTC 86 indicated with DTC 138 at the same time?

YES -Do the DTC 86 troubleshooting (see DTC 86: F-CAN COMMUNICATION MALFUNCTION ).

NO -Go to step 3.
Turn the ignition switch to LOCK (0).
Check the No. 11 (15 A) fuse in the main under-hood fuse box.
Is the fuse blown?

YES -Replace the fuse, and recheck. If the fuse is blown, check for a short to body ground in this fuse circuit.

NO -Reinstall the checked fuse, then go to step 5.
Disconnect the brake pedal position switch 4P connector (see step 2 under BRAKE PEDAL AND BRAKE PEDAL POSITION SWITCH ADJUSTMENT ).
Measure the voltage between brake pedal position switch 4P connector terminal No. 1 and body ground.

Fig 1: Measuring Voltage Between Brake Pedal Position Switch 4P Connector Terminal No. 1 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES -Go to step 7.

NO -Repair an open in the wire between the No. 11 (15 A) fuse in the main under-hood fuse box and the brake pedal position switch.
Short the SCS line with the HDS.
Disconnect the PCM connector A (49P).
Check for continuity between brake pedal position switch 4P connector terminal No. 2 and PCM connector A (49P) terminal No. 8.

Fig 2: Checking Continuity Between Brake Pedal Position Switch 4P Connector Terminal No. 2 And PCM Connector A (49P) Terminal No. 8
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Go to step 10.

NO -Repair an open in the wire between the PCM and the brake pedal position switch.
Reconnect all connectors.
Do the brake pedal position switch test (see HIGH MOUNT BRAKE LIGHT REPLACEMENT ).
Is the switch OK?

YES -Go to step 12.

NO -Replace the brake pedal position switch (see BRAKE PEDAL AND BRAKE PEDAL POSITION SWITCH ADJUSTMENT ).
Update the PCM if it does not have the latest software (see KNOCK SENSOR REPLACEMENT ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ).
Turn the ignition switch to ON (II).
Clear the DTC with the HDS.
Start the engine, then press the brake pedal slowly and hard.
Check for DTCs with the HDS.
Is DTC 138 indicated?

YES -Check for loose terminals in the PCM connector A (49P). If the PCM was updated, substitute a known-good PCM (see SUBSTITUTING THE PCM ), then retest. If the PCM was substituted, go to step 17.

NO -If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM (see PCM REPLACEMENT ).
Substitute a known-good brake pedal position switch (see BRAKE PEDAL AND BRAKE PEDAL POSITION SWITCH ADJUSTMENT ).
Turn the ignition switch to ON (II).
Clear the DTC with the HDS.
Start the engine, then press the brake pedal firmly.
Is DTC 138 indicated?

YES -Check for loose terminals in the brake pedal position switch connector, then go to step 21.

NO -Replace the brake pedal position switch (see BRAKE PEDAL AND BRAKE PEDAL POSITION SWITCH ADJUSTMENT ).
Update the VSA modulator-control unit if it does not have the latest software (see VSA MODULATOR-CONTROL UNIT UPDATE ).
Start the engine, then press the brake pedal slowly and hard.
Check for DTCs with the HDS.
Is DTC 138 indicated?

YES -Check for loose terminals in the VSA modulator-control unit 46P connector. If the VSA modulator-control unit was updated and the symptom/indication is still present, replace the VSA modulator-control unit (see VSA MODULATOR-CONTROL UNIT REMOVAL AND INSTALLATION ).

NO -If the VSA modulator-control unit was updated, troubleshooting is complete. If any other DTCs are indicated, go to the indicated DTCS TROUBLESHOOTING .