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.

Enter this TEST only when directed by TEST AA, TEST C or TEST PA.

This test is intended to diagnose:

Power Control Module (PCM).
Main relay.
Ignition switch.
Wiring harness circuits (SIG RTN, PWR GND, VPWR, KAPWR and VREF).

To prevent replacement of good components, be aware the following non-EEC related areas and components may be cause of problem:

Battery cables and ground straps.
Voltage regulator.
Generator.
Ignition switch.

CAUTION: When battery is disconnected, PCM may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle.

1) Battery Voltage Check Turn ignition on. Measure battery voltage. If voltage is less than 10.5 volts, recharge or replace battery. If voltage is 10.5 volts or more, go to next step.

2) Check PWR GND Circuit Continuity 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 connected. Measure resistance between test pins No. 40 and 60 at breakout box and negative battery terminal. If one or both readings are 5 ohms or more, repair open in PWR GND circuit. Remove breakout box, reconnect components and repeat QUICK TEST. If both readings are less than 5 ohms, go to next step.

3) Check For Open Between SIG RTN & PWR GND Circuits At PCM Turn ignition off. With breakout box installed and PCM connected, set DVOM on 200-ohm scale. Measure resistance between test pin No. 46 and test pins No. 40 and 60 at breakout box. If one or both readings are 5 ohms or more, replace PCM. Remove breakout box and repeat QUICK TEST. If both readings are less than 5 ohms, go to next step.

4) Check SIG RTN Circuit Continuity Turn ignition off. Measure resistance between test pin No. 46 at breakout box and SIG RTN terminal at Data Link Connector (DLC). If resistance is 5 ohms or more, repair open in SIG RTN circuit. Remove breakout box, reconnect components and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.

5) Check KAPWR Circuit Voltage At Main Relay Turn ignition off. Locate main fuse block in engine compartment, on left inner fender panel. Remove main relay. Turn ignition on. Measure voltage between negative battery terminal and KAPWR terminal at main relay connector. If voltage is 10.5 volts or less, check KAPWR circuit between main relay and positive battery terminal for open circuit. If voltage is 10.5 volts or more, go to next step.

NOTE: Vehicles equipped with Power Distribution Boxes use a diode to provide electrical surge protection for the ignition switch and Ignition Control Module (ICM). If a no-start/no-code condition exists, ensure diode continuity is present in one direction only before going to step 6).

6) Check Ignition Circuit Voltage At Main Relay Connect PCM to breakout box. Remove main relay. Turn ignition on. Measure voltage between negative battery terminal and IGN terminal at main relay connector. If voltage is less than 10.5 volts, repair open in IGN circuit. Remove breakout box, reconnect components and repeat QUICK TEST. If voltage is 10.5 volts or more, go to next step.

7) Check PWR GND Circuit Continuity Turn ignition off. With PCM connected to breakout box, measure resistance between negative battery terminal and PWR GND terminal at main relay connector. If resistance is 10 ohms or more, repair open circuit. Remove breakout box, reconnect components and repeat QUICK TEST. If reading is less than 10 ohms, go to next step.

8) Check VPWR Circuit Continuity Turn ignition off. Measure resistance between test pins No. 37 and 57 (VPWR) at breakout box and VPWR terminal at main relay connector. If resistance is 5 ohms or more, repair open in VPWR circuit between main relay and PCM. Remove breakout box, reconnect components and repeat QUICK TEST. If resistance is less than 5 ohms, go to next step.

9) Check VPWR Circuit Voltage Turn ignition off. Install main relay. Turn ignition on. With PCM connected, measure voltage between test pins No. 37 and 57 (VPWR) and test pins No. 40 and 60 (PWR GND) and 46 (SIG RTN) at breakout box. If voltage is 10.5 volts or more, repair circuit between PCM and main relay. Remove breakout box, reconnect components and repeat QUICK TEST. If voltage is less than 10.5 volts, replace main relay. Remove breakout box, reconnect components and repeat QUICK TEST.