Diagnostic Aids

1999 Mazda 626 ES, 2.5 D, StandardSECTION Diagnostic Aids

KAPWR is interrupted when PCM or battery is disconnected. DTC P0603 may be generated during the next PCM power-up.

This test is used to diagnose the following:

  • Battery terminal condition.
  • Keep Alive Power (KAPWR) circuit routing.
  • KAPWR circuit condition.
  • Faulty Powertrain Control Module (PCM).

  1. Check Battery Terminals

    Ensure freeze frame data is recorded. Inspect battery terminals for corrosion or loose connection. Service or replace as necessary. If battery terminals are okay, go to next step.
  2. Check Wiring Harness

    Inspect wiring harness and connectors for damage or corrosion. Ensure wiring harness is not routed too close to ignition or exhaust components. Service or replace if necessary. If wiring harness looks okay, go to next step.
  3. Check KAPWR Circuit

    Turn ignition off. Disconnect PCM 104-pin connector. Inspect pins for damage. Install Breakout Box (014-00950), leaving PCM disconnected. Connect DVOM between test pin No. 55 (KAPWR) and test pins No. 51 and 103 (PWR GND) at breakout box. Shake and bend small sections of wiring harness between PCM and dash panel. If voltage is continuously 10.5 volts or more, go to next step. If voltage drops to less than 10.5 volts, isolate open in KAPWR circuit and repair as necessary. Repeat QUICK TESTΒ .
  4. Check For DTC P0603/P0605

    Perform KOEO self-test. If DTC P0603 and/or P0605 is present, replace PCM and repeat QUICK TESTΒ . If any other DTCs are present, service as necessary. If no trouble codes are present, testing is complete.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.