Diagnostic Procedures
WARNING: This page is about a different car, the 2002 Mazda B4000, 2002 Mazda B3000, and 2002 Mazda B2300. However, it is still accessible from the selected car via links, so may be relevant.
- If QUICK TEST was not performed, go to QUICK TEST
under SELF-DIAGNOSTIC SYSTEM. If QUICK TEST was performed, go to next step.NOTE: If rear HO2S electrical connections are interchanged (crossed), the catalyst efficiency monitor test will fail.
- Check Rear HO2S Wiring & PCM Connections
Inspect wiring of rear HO2S for proper routing and connection. Disconnect PCM connector. Inspect PCM connector for damaged or pushed out pins, corrosion and loose wires. If any problems are found with HO2S wiring or PCM connector, repair as necessary. Go to step 10 . If no problems are found, go to next step.WARNING: Fuel system remains pressurized with engine off. - Check Fuel Pressure
Turn ignition off. Install a fuel pressure gauge. Start engine and idle. Record fuel pressure. Increase engine speed to 2500 RPM and hold for one minute. Record fuel pressure. See FUEL PRESSURE SPECIFICATIONS table. If fuel pressure is within specification, fuel pressure is okay. Remove fuel pressure gauge. Go to next step. If fuel pressure is not within specification, go to FUEL DELIVERY SYSTEM under SYSTEM TESTS.FUEL PRESSURE SPECIFICATIONSEngine psi (kPa) 2.3L 35-55 (240-380) 3.0L & 4.0L 30-65 (207-448) - Check For Obvious Leak Sources In Exhaust System
Turn ignition off. Inspect complete exhaust system for leaks, cracks, loose connections and punctures. If no problems are found, go to next step. If a problem is found, repair as necessary. Go to step 10 . - Check For Obvious Restrictions In Exhaust System
Inspect exhaust system for dents or collapsed areas. If exhaust system is okay, go to next step. If exhaust system is not okay, repair or replace components as necessary. Go to step 10 .NOTE: During exhaust system restriction check, vacuum gauge reading may be normal when engine is first started and idling. An excessive exhaust restriction will cause vacuum gauge needle to drop low even with engine idling. - Check Manifold Vacuum For Indication Of Excessive Exhaust System Restriction
Attach a vacuum gauge to intake manifold vacuum source. Using scan tool, monitor engine RPM. Observe vacuum gauge while gradually increasing engine speed to 2000 RPM with transmission in neutral. Turn ignition off. If vacuum rose to more than 16 in. Hg with engine speed at 2000 RPM, go to next step. If vacuum did not rise to more than 16 in. Hg with engine speed at 2000 RPM, manifold vacuum did not attain an acceptable level. Check for an exhaust restriction. Go to step 8 - Check Manifold Vacuum For Indication Of Moderate Exhaust System Restriction
With KOER, gradually increase engine speed from idle to 2000 RPM. Observe rate of speed the vacuum gauge needle rises while maintaining increased engine RPM. Observe vacuum gauge for the following conditions:- On a non-restricted exhaust system, vacuum gauge needle will quickly rise to normal range as increased RPM is maintained.
- On a restricted exhaust system, vacuum gauge needle will slowly rise to normal range as increased RPM is maintained.
NOTE: An intake manifold gasket leak may cause vacuum gauge needle to remain well below normal range. - Check Manifold Vacuum With Exhaust Manifold Disconnected For Indication Of Restriction
Turn ignition off. Disconnect exhaust system at exhaust manifold flange. Repeat vacuum measurement in step 7 . If vacuum gauge needle quickly rises to more than 16 in. Hg (54 kPa) with engine speed at 2000 RPM, an exhaust restriction is downstream of exhaust manifold. Reconnect exhaust manifold. Go to next step. If vacuum gauge needle does not quickly rise to more than 16 in. Hg (54 kPa) with engine speed at 2000 RPM, an exhaust restriction is present in the exhaust manifold. Remove vacuum gauge and tachometer. Using a length of chain, inspect each exhaust manifold port for casting flash/restrictions. DO NOT use a wire or light to check ports. A restriction may be small enough for both to pass through, but large enough to cause excessive backpressure with high engine RPM. If unable to remove excess flash/restriction, replace exhaust manifold. Go to step 10 . - Check Manifold Vacuum With Muffler/Tailpipe Assembly Disconnected For Indication Of Restriction
Turn ignition off. Disconnect muffler/tailpipe assembly at catalytic converter. Repeat vacuum measurement in step 7 . If vacuum gauge needle quickly rises to more than 16 in. Hg (54 kPa) with engine speed at 2000 RPM, an exhaust restriction is in muffler/tailpipe assembly. Replace muffler/tailpipe assembly. Go to next step. If vacuum gauge needle does not quickly rise to more than 16 in. Hg (54 kPa) with engine speed at 2000 RPM, an exhaust restriction is present in the catalytic converter. Remove vacuum gauge and tachometer. Replace catalytic converter. Go to next step. - Drive Cycle
Reconnect all electrical connectors. Using scan tool, clear DTC memory. Perform CATALYST MONITOR REPAIR VERIFICATION DRIVE CYCLE in MONITOR REPAIR VERIFICATION DRIVE CYCLES under DRIVE CYCLE PROCEDURES. Using scan tool, retrieve DTCs. If same DTC is not present, go to next step. If same DTC is present, replace faulty PCM. Go to next step. - Verify Trouble Shooting Of DTCs Completed
Perform QUICK TEST under SELF-DIAGNOSTIC SYSTEM. If same DTC is present, replace faulty PCM. Repeat QUICK TEST under SELF-DIAGNOSTIC SYSTEM. If any other DTC is present, go to applicable procedure for other DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are set, trouble shooting is complete.