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Home >> Acura >> 2003 >> MDX Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Performance System Self-Diagnostics >> Diagnostic Tests >> DTC P0138 Or DTC P0158
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DTC P0138 Or DTC P0158

Code Definition

CAUTION: When substituting or replacement of PCM is recommended, see PCM REMOVAL & REPLACEMENT  for important precautions.
NOTE: This test covers both Front and Rear Air Fuel Ratio (A/F) sensors. The information will be shown Rear (Bank 1) first and Front (Bank 2) second. When discussion of PCM harness connector terminals arises, Rear (A/F) ratio sensor terminals will precede Front A/F ratio sensor terminals. Also, Front A/F ratio sensor terminal information will be enclosed in parantheses ( ).
  1. Turn ignition on. Using Honda PGM Tester or the HDS, do the DTC CLEAR in the CLEAR menu.
  2. Start engine. Hold engine at 3000 RPM with no load in (Park or Neutral) until the radiator fan comes on, then let engine idle.
  3. Using Honda PGM Tester or the HDS, check the AF FB AVE (LT FUEL TRIM) in the DATA list. If the value is 1.00 or more, go to next step. If the value is not 1.00 or more, check for poor connections or loose terminals at secondary HO2 sensor (Sensor 2) and PCM connectors. Go to step  1 .
  4. Using Honda PGM Tester or the HDS, check the HO2S S2 in the DATA list. If the voltage is 0.75 volt or more, go to step  7 . If the voltage is not 0.75 volt or more, go to next step.
  5. Test drive vehicle under the following conditions:
    • Engine coolant temperature more than 158°F (70°C).
    • A/T in "D" position.
    • Engine speed at 2000-3000 RPM.
    • Drive vehicle about 10 minutes, then decelerate (with throttle fully closed) for 5 seconds.
  6. Using the Honda PGM Tester or the HDS, monitor OBD STATUS for DTCs P0138 and/or (P0158) in the DTCs menu. If it is PASSED, problem is intermittent, system is OK at this time. If it FAILED, go to step  12 . If it is EXECUTING, continue driving condition until a result comes in. If it is OUT OF CONDITION, go to step  5 and recheck.
  7. Turn ignition off. Disconnect the secondary HO2S (Sensor 2) 4-pin connector. See Figure . Go to next step.
  8. With a fused jumper wire, connect secondary HO2S (Sensor 2) 4-pin connector terminals No. 1 and 2. Go to next step.
  9. Turn ignition on. Using Honda PGM Tester or the HDS, check the HO2S S2 in the DATA list. If the voltage is 0.75 volt or more, go to next step. If the voltage is not 0.75 volt or more, go to step  12 .
  10. Turn ignition off. Disconnect PCM harness connector "A". See Figure . Check for continuity between PCM harness connector "A" terminals A21 and A28 and/or (A22) and A28. If there is continuity, go to step  19 . If there is no continuity, go to next step.
  11. Remove the jumper wire connected to secondary HO2S (Sensor 2) 4-pin connector. Check for continuity between PCM harness connector "A" terminals A21 (A22) and secondary HO2S (Sensor 2) 4-pin connector terminals No. 1. If there is continuity, repair open in wire between PCM harness connector "A" terminal A28 and secondary HO2S (Sensor 2). Go to step  14 . If there is no continuity, repair wire between PCM harness connector "A" terminals A21 (A22) and secondary HO2S (Sensor 2). Go to step  14 .
  12. Turn ignition off.
  13. Replace secondary HO2S (Sensor 2).
  14. Turn ignition on. With the Honda PGM tester or the HDS, do PCM RESET in the CLEAR menu. Do the PCM idle learn procedure. See PCM IDLE LEARN PROCEDURE  .
  15. Start engine. Hold engine at 3000 RPM with no load in (Park or Neutral) until the radiator fan comes on, then let engine idle.
  16. Test drive vehicle under the following conditions:
    • Engine coolant temperature more than 158°F (70°C).
    • A/T in "D" position.
    • Engine speed at 2000-3000 RPM.
    • Drive vehicle about 10 minutes, then decelerate (with throttle fully closed) for 5 seconds.
  17. Check for Temporary DTCs or DTCs in the DTC menu. If DTCs P0138 and/or (P0158) are set, check for poor connections or loose terminals at secondary HO2S (Sensor 2) and PCM connector, go to step  1 . If any other Temporary DTCs or DTCs are set, troubleshoot those indicated. If there are no Temporary DTCs or DTCs set, go to next step.
  18. Using the Honda PGM Tester or the HDS, monitor OBD STATUS for P0138 and/or (P0158) in the DTCs menu. If it is PASSED, troubleshooting is complete. If it FAILED, check for poor connections or loose terminals at secondary HO2S (Sensor 2) and PCM connector Go to step  1 . If it is NOT COMPLETED, go to step  14 and recheck.
  19. Update the PCM if it does not have the latest software, or substitute a know-good PCM.
  20. Start engine. Hold engine at 3000 RPM with no load in (Park or Neutral) until the radiator fan comes on, then let engine idle
  21. Test drive vehicle under the following conditions:
    • Engine coolant temperature more than 158°F (70°C).
    • A/T in "D" position.
    • Engine speed at 2000-3000 RPM.
    • Drive vehicle about 10 minutes, then decelerate (with throttle fully closed) for 5 seconds.
  22. Check for Temporary DTCs or DTCs in the DTC menu. If DTC P0138 and/or (P0158) are set, check for poor connections or loose terminals at secondary HO2S (Sensor 2) and PCM connectors. Go to step  1 . If any other Temporary DTCs or DTCs are set, troubleshoot those indicated. If Temporary DTCs or DTCs are not set, PCM was updated, troubleshooting is done. If PCM was substituted, replace the original PCM.
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