Home ReviewsRefund
Home/Honda/Pilot/Honda Pilot I (2002-2005)/Repair manual/Testing & Diagnostics/DTC P0128: Cooling System Malfunction
Contents Wiring diagrams Section: Testing & Diagnostics All sections

DTC P0128: Cooling System Malfunction Honda Pilot I

Testing & Diagnostics 3 illustrations ~761 words

Note. If the DTCs listed below are stored at the same time as DTC P0128, troubleshoot those DTCs first, then recheck for P0128.

P0107, P0108, P1128, P1129: Manifold Absolute Pressure (MAP) sensor

P1106, P1107, P1108: Barometric Pressure (BARO) sensor

P1259: VTEC system

P0401: Exhaust Gas Recirculation (EGR) System Flow

P0116, P0117, P0118: Engine Coolant Temperature (ECT) sensor

P0112, P0113: Intake Air Temperature (IAT) sensor

P0335, P0336: Crankshaft Position (CKP) sensor

P0300: Random misfire

P0301, P0302, P0303, P0304, P0305, P0306: No. 1, No. 2, No. 3, No. 4, No. 5 or No. 6 cylinder misfire

P0505: Idle control system

P1519: Idle Air Control (IAC) valve

DTC P0128 can occasionally set when the hood is opened while the engine is running.

  1. Turn the ignition switch ON (II).
  2. Check the radiator fan. Does the radiator fan keep running? YES -Check the radiator fan circuit (see «ELECTRIC COOLING FANS»(ref-166089) ), the radiator fan switch circuit (see «ELECTRIC COOLING FANS»(ref-166089) ), and the radiator fan switch (see «ELECTRIC COOLING FANS»(ref-166089) ). If they are OK, substitute a known-good PCM and recheck (see «HOW TO SUBSTITUTE THE PCM FOR TESTING»(ref-173995-S22023424662005041500000) ). If the symptom/indication goes away, replace the original PCM. NO -Go to step 3.
  3. Reset the PCM (see «HOW TO RESET THE PCM»(ref-173995-S09390407622005041500000) ).
  4. Start the engine. Hold the engine at 3,000 rpm with no load (in Park or neutral) until the radiator fan comes on. Is DTC P0128 indicated? YES -Test the thermostat (see «THERMOSTAT TEST»(ref-173994-S40767114182005041500000) ). NO -Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the radiator fan sensor and the PCM.

Scheme 94

Scheme 94: DTC P0131: Primary HO2S (Sensor 1) Circuit Low Voltage
Scheme 94: DTC P0131: Primary HO2S (Sensor 1) Circuit Low Voltage
  1. Reset the PCM (see «HOW TO RESET THE PCM»(ref-173995-S09390407622005041500000) ).
  2. Start the engine. Hold the engine at 3,000 rpm with no load (in Park or neutral) until the radiator fan comes on.
  3. Check the primary HO2S (Sensor 1) output voltage with the scan tool or the HDS during acceleration using wide open throttle. Does the voltage stay at 0.5 V or less? YES -Go to step 4. NO -Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the primary HO2S (Sensor 1) and at the PCM.
  4. Check the fuel pressure (see «FUEL PRESSURE TEST»(ref-174005-S08926900662005042700000) ). Is it normal? YES -Go to step 5. NO -Repair the fuel supply system.
  5. Turn the ignition switch OFF.
  6. Disconnect the primary HO2S (Sensor 1) 4P connector.
  7. Start the engine, and let it idle.
  8. Check the primary HO2S (Sensor 1) output voltage with the scan tool or the HDS. Does it stay at 0.5 V or less? YES -Go to step 9. NO -Replace the primary HO2S (Sensor 1).
  9. Turn the ignition switch OFF.
  10. Disconnect the PCM connector C (31P).
  11. Check for continuity between primary HO2S (Sensor 1) 4P connector terminal No. 1 and body ground. Is there continuity? YES -Repair short in the wire between the PCM (C16) and the primary HO2S (Sensor 1). NO -Substitute a known-good PCM and recheck (see «HOW TO SUBSTITUTE THE PCM FOR TESTING»(ref-173995-S22023424662005041500000) ). If the symptom/indication goes away, replace the original PCM.

Scheme 95

Scheme 95: DTC P0132: Primary HO2S (Sensor 1) Circuit High Voltage
Scheme 95: DTC P0132: Primary HO2S (Sensor 1) Circuit High Voltage

Scheme 96

Scheme 96
Scheme 96
  1. Reset the PCM (see «HOW TO RESET THE PCM»(ref-173995-S09390407622005041500000) ).
  2. Start the engine. Hold the engine at 3,000 rpm with no load (in Park or neutral) until the radiator fan comes on.
  3. Check the primary HO2S (Sensor 1) output voltage with the scan tool or the HDS. Does the voltage stay at 0.9 V or more? YES -Go to step 4. NO -Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the primary HO2S (Sensor 1) and at the PCM.
  4. Turn the ignition switch OFF.
  5. Disconnect the primary HO2S (Sensor 1) 4P connector.
  6. Connect primary HO2S (Sensor 1) 4P connector terminals No. 1 and No. 2 with a jumper wire.
  7. Turn the ignition switch ON (II).
  8. Check the primary HO2S (Sensor 1) output voltage with the scan tool or the HDS. Is there 0.9 V or more? YES -Go to step 9. NO -Replace the primary HO2S (Sensor 1).
  9. Turn the ignition switch OFF.
  10. Connect PCM connector terminals C16 and C18 with a jumper wire.
  11. Turn the ignition switch ON (II).
  12. Check the primary HO2S (Sensor 1) output voltage with the scan tool or the HDS. Is there 0.9 V or more? YES -Substitute a known-good PCM and recheck (see «HOW TO SUBSTITUTE THE PCM FOR TESTING»(ref-173995-S22023424662005041500000) ). If the symptom/indication goes away, replace the original PCM. NO -Repair open in the wire between the PCM (C16, C18) and the primary HO2S (Sensor 1).

More articles — Pgm-Fi System