Diagnostic Aids

WARNING: This page is about a different car, the 1995 Mazda MX-6 and 1995 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.

Perform this test when directed by QUICK TEST. This test is intended to diagnose a faulty brakelight circuit or PCM. To prevent replacement of good components, be aware following non-EEC related areas may be at fault:

Brakelight bulb.
Brake switch or brakelight fuse.

1) KOER Code 536: Verify Brake Pedal Was Depressed Code 536 indicates that when brake pedal is applied during KOER SELF-TEST, brake switch signal did not cycle high and low. Possible causes for this fault are:

Brake pedal not applied during self-test.
Brake pedal applied during entire self-test.
Open brakelight circuit.
Short to ground or power.
Faulty brake switch.
Faulty Powertrain Control Module (PCM).

If brake was not applied during KOER SELF-TEST, repeat test. Depress and release brake pedal only once during test. If pedal was depressed, go to next step.

2) Check Operation Of Brakelights With ignition on, check operation of brakelights. If brakelights operate normally, go to next step. If brakelights do not operate, go to step 4). If brakelights are always on, go to step 5).

3) Check For Brake Switch Circuit Cycling Turn ignition off. Disconnect PCM 60-pin connector and inspect for damaged pins, corrosion and loose wires. Repair as necessary. Install Breakout Box (49-UN01-058), leaving PCM disconnected. Measure voltage between brake switch test pin (No. 2) and test pin No. 40 at breakout box while applying and releasing brake. If voltage cycles, replace PCM and repeat QUICK TEST. If voltage does not cycle, repair open circuit in brake switch circuit between PCM and brake switch connection to brakelight circuit. Repeat QUICK TEST.

4) Check For Power To Brake Switch Ensure related fuses andbrakelight bulbs are in good condition. Turn ignition off. Disconnect brake switch (located on brake pedal). Measure voltage between BATT (+) input to brake switch and ground. If voltage is more than 10 volts, check condition of brake switch. If brake switch is okay, repair open circuit between brake switch and brakelight ground. Repeat QUICK TEST. If voltage is less than 10 volts, repair open BATT (+) circuit to brake switch and repeat QUICK TEST.

5) Verify Brake Switch Is Not Always Closed Turn ignition off. Disconnect brake switch (located on brake pedal). Turn ignition on. If brakelights are still on, go to next step. If brakelights are not on, verify correct installation of brake switch. If installation is okay, replace brake switch and repeat QUICK TEST.

6) Check For Short To Power In PCM Turn ignition off. Disconnect PCM. Turn ignition on. Check brakelights. If brakelights are on, go to next step. If brakelights are off, replace PCM and repeat QUICK TEST.

7) Check For Short To Power In Shift Lock Actuator Turn ignition off. Disconnect brake switch. Disconnect PCM. Disconnect shift lock actuator, cruise control module and ABS module (if equipped). Turn ignition on. If brakelights are still on, repair short to power in brake switch orbrakelight circuit and repeat QUICK TEST. If brakelights are off, repair short circuit in shift lock actuator circuit, cruise control system circuit or ABS circuit. Reconnect all components and repeat QUICK TEST.