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.
- Check For Source Of Potential HO2S Contamination
Inspect vehicle for use of unapproved silicone sealers, fuel contaminated with silicone additives, excessive oil burning, engine internal coolant leak, lead contaminated fuel, short drive cycles in cold weather and use of unapproved cleaning agents. If any of these conditions are not present, go to next step. If any of these conditions are present, repair contamination source. Replace HO2S, engine oil and filter. Go to step 8 . - Check For Unmetered Air Leaks
Fuel mixture can be affected by unmetered air leaks. Inspect air intake system for leaks. Check MAF sensor assembly, hoses to throttle body, intake manifold gaskets, PCV system, disconnected vacuum lines, improperly seated oil dipstick and oil filler cap. Also check exhaust system for leaks at flanges and gaskets. If leaks are not present, go to next step. If leaks are present, repair leak. Go to step 8 . - Check HO2S Circuit Wiring With PCM Connected
Disconnect suspect HO2S. Jumper HO2S SIG circuit (DTC P0133, Gray/Light Blue wire) or (DTC P0153, Red/Black wire) to VPWR circuit (DTC P0133 or DTC P0153 Light Blue/Orange wire) at HO2S harness connector. See Fig 1 . With KOEO, using scan tool access O2S11 (DTC P0133) or O2S21 (DTC P0153). Record voltage. If voltage is more than 1.5 volts, go to next step. If voltage is 1.5 volts or less, remove jumper. Go to step 6 . - Check For Short To VPWR & VREF Circuits
Disconnect scan tool from DLC. With KOEO, measure voltage of HO2S SIG circuit (DTC P0133, Gray/Light Blue wire) or (DTC P0153, Red/Black wire) and SIG RTN circuit (Orange wire) at suspect HO2S harness connector. See Fig 1 . If voltage is less than 4.5 volts, replace faulty HO2S, engine oil and filter. Go to step 8 . If voltage is 4.5 volts or more, repair short to VPWR or VREF circuit. See WIRING DIAGRAMS article. Go to step 8 . - Check Resistance Of HO2S Signal Circuit
Turn ignition off. Disconnect PCM connector. Install breakout box, leaving PCM disconnected. Measure resistance of HO2S SIG circuit between breakout box terminal No. 60 (DTC P0133) or terminal No. 87 (DTC P0153) and HO2S harness connector (DTC P0133, Gray/Light Blue wire) or (DTC P0153, Red/Black wire). See Fig 1 . Record reading. Measure resistance of HO2S SIG RTN circuit between breakout box terminal No. 91 and HO2S harness connector (Orange wire). Record reading. If each resistance measurement is less than 5 ohms, go to next step. If either resistance measurement is 5 ohms or more, repair open circuit. See WIRING DIAGRAMS article. Go to step 8 . - Check For Short To VPWR
Disconnect scan tool from DLC. Measure resistance of HO2S SIG circuit between breakout box terminals No. 60 (DTC P0133) or terminal No. 87 (DTC P0153) and breakout box terminal No. 71/97. If resistance is 10,000 ohms or less, repair short circuit. See WIRING DIAGRAMS article. Go to step 9 . If resistance is more than 10,000 ohms, replace faulty PCM. Go to step 9 . - Drive Cycle
Reconnect all electrical connectors. Using scan tool, clear DTC memory. Perform HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE or FUEL OR MISFIRE 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
Make sure all electrical connectors are reconnected. Clear DTCs from PCM memory using scan tool. Perform QUICK TEST under SELF-DIAGNOSTIC SYSTEM. If any DTC is present, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are present, test is complete.