LEMON Manuals: Even more car manuals for everyone
Home >> Mazda >> 1999 >> B2500 SX, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 4 (Engine Controls - Self-Diagnostics - EEC-V - 6.8L (99S E Series & 99S F350 To F550)) >> System Tests >> Test JH: Tachometer Output Failure >> Diagnostic Aids

Diagnostic Aids

WARNING: This page does not describe the selected car, but rather 26 other vehicles, including the 1999 Mercury Tracer, 1999 Mercury Sable, 1999 Mercury Mystique, 1999 Mercury Mountaineer, and 1999 Mercury Grand Marquis. However, it is still accessible from the selected car via links, so may be relevant.

Perform this test when instructed to or if directed by other test procedures. This test is used to diagnose the Powertrain Control Module (PCM):

  1. Check CTO Circuit For Short To Power

    Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Turn ignition on. Measure voltage between PCM connector pin No. 48 and chassis ground. If voltage is less than .5 volt, go to next step. If voltage is .5 volt or more, repair short to power in CTO circuit.

  2. Check CTO Circuit For Short To Ground

    Turn ignition off. Disconnect instrument cluster connector. Measure resistance between PCM connector pin No. 48 and chassis ground. If resistance is more than 10,000 ohms, go to next step. If resistance is 10,000 ohms or less, repair short to ground in CTO circuit.

  3. Check For Open CTO Circuit

    Measure resistance of CTO circuit between PCM connector pin No. 48 and instrument cluster wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open CTO circuit.

  4. Check CTO Signal From PCM

    Reconnect PCM connector. Start engine. Measure voltage between CTO terminal at instrument wiring harness connector and chassis ground. If voltage is not 3-9 volts, replace PCM. If voltage is 3-9 volts, CTO signal from PCM is okay. Check instrument cluster and repair as necessary. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT in appropriate lemon-25® manual.
scientia non olet · About LEMON Manuals