Mazda DTC C1446 Diagnostic

DTC C1446 Brake switch
DETECTION CONDITION

• Brake switch ON signal is input for 6 min or more when driving at a vehicle speed of 20 km/h {12.4 mph} or more.

• Brake switch ON signal is not input even though the DSC HU/CM determines vehicle deceleration.
POSSIBLE CAUSE

• Open or short circuit in the wiring harness between brake switch and the terminal on the PJB

• Open or short circuit in the wiring harness between the terminals on the PJB and PCM

• Brake switch malfunction

• Poor connection at connectors (female terminal)

Diagnostic procedure

 
 

STEP

 

 

INSPECTION

 

 

ACTION

 

1
VERIFY OPEN OR SHORT CIRCUIT IN BRAKE SWITCH SIGNAL

• Turn the ignition switch to the ON position.

• Measure the voltage between the following PCM terminals and body ground when the brake pedal is depressed and released:

– PCM (ZJ, Z6): 1V-Body ground

– PCM (LF): 1AU-Body ground

Voltage

Brake pedal depressed: B+

Brake pedal released:

1 V or less

Yes

Go to Step 5.

No

If it is B+ under any condition, then go to the next step.

If it is 1 V or less under any condition, then go to Step 3.

2
INSPECT BRAKE SWITCH SIGNAL FOR SHORT TO POWER SUPPLY CIRCUIT

• Disconnect the brake switch connector.

• Measure voltage between the brake switch connector terminal D (vehicle harness-side) and body ground.

• Is the voltage 1 V or less?

Yes

Go to Step 4.

No

Repair or replace the wiring harness between the PCM and brake switch, then go to Step 5.

3
INSPECT BRAKE SWITCH SIGNAL FOR OPEN CIRCUIT

• Disconnect the PCM connectors.

• Disconnect the brake switch connector.

• Inspect continuity between the following PCM connector terminals (vehicle harness-side) and brake switch terminal D:

– PCM (ZJ, Z6): 1V

– PCM (LF): 1AU

• Is there continuity?

Yes

Go to the next step.

No

Repair or replace the wiring harness between the PCM and brake switch, then go to Step 5.

4
INSPECT BRAKE SWITCH

• Inspect the brake switch.

• Is the brake switch normal?

Yes

Go to the next step.

No

Replace the brake switch, then go to the next step.

5
VERIFY THAT THE SAME DTC IS NOT PRESENT

• Reconnect all disconnected connectors.

• Clear the DTCs from the memory.

• Start the engine and drive the vehicle at 20 km/h {12.4 mph} or more.

• Are the same DTCs present?

Yes

Repeat the inspection from Step 1.

If the malfunction recurs, replace the DSC HU/CM, then go to the next step.

No

Go to the next step.

6
VERIFY THAT NO OTHER DTCS ARE PRESENT

• Are any other DTCs output?

Yes

Go to the applicable DTC inspection.

No

DTC troubleshooting completed.
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