What are these codes PO175 & PO172?
03-29-2005, 02:30 PM
#5
P0172 or 175
CIRCUIT DESCRIPTION
The PCM controls a Closed Loop air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. The PCM monitors the heated oxygen sensor signal voltage and adjusts the fuel delivery based on the signal voltage while in Closed Loop. A change made to the fuel delivery changes the Long and Short Term Fuel Trim values. The Short Term Fuel Trim values change rapidly in response to the HO2S signal voltages. These changes fine tune the engine fueling. The Long Term Fuel Trim values change in response to trends in Short Term Fuel Trim. The Long Term Fuel Trim makes coarse adjustments to fueling in order to re-center and restore control to Short Term Fuel Trim. You can use a scan tool in order to monitor the Short and Long Term Fuel Trim. The ideal fuel trim values are around 0 percent . A positive Fuel Trim value indicates that the PCM is adding fuel in order to compensate for a lean condition. A negative Fuel Trim value indicates that the PCM is reducing the amount of fuel in order to compensate for a rich condition. If the PCM detects an excessively Rich or Lean condition, the PCM sets a DTC. The long term fuel trim diagnostic parameter is an average of several of the long term speed load learn cells which the PCM selects based on the engine speed and the engine load.
CONDITIONS FOR RUNNING THE DTC
DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0200, P0300, P0335, P0336, P0351-P0358, P0405, P0410, P0412, P0418, P0443, P0500, P0502, P0503, P1258, P1404, P1415, P1416 not set.
The engine coolant temperature is between 50°C (122°F) and 115°C (239°F).
The barometric pressure is more than 74 kPa.
The mass air flow is between 5.0 g/s and 90 g/s.
The manifold absolute pressure is between 26 kPa and 90 kPa.
The intake air temperature is between -20°C (-4°F) and 90°C (194°F).
The engine speed is between400 RPM and 3,000 RPM.
The TP sensor angle is less than 90 percent.
The vehicle speed is less than 137 km/h (85 mph).
CONDITIONS FOR SETTING THE DTC
The average Long Term Fuel Trim cell values are below a predetermined threshold.
All the above conditions are present for 40 seconds.
ACTION TAKEN WHEN THE DTC SETS
The PCM illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails, if the diagnostic fails under the same conditions (load, RPM, temperature, etc.) as the previous ignition cycle that the test ran and failed.
The first time the diagnostic fails, the PCM records the operating conditions in Failure Records.
The second consecutive ignition cycle that this diagnostic fails [under the same conditions (load, RPM, temperature, etc.) as the previous ignition cycle that the test ran and failed], the PCM stores this information in Freeze Frame. The PCM copies any data previously stored in Freeze Frame and copies the data into the Failure Records. The PCM then overwrites the Freeze Frame. The only exception to this is if a Misfire DTC was already recorded in Freeze Frame. In this case, the Misfire data stays in Freeze Frame and the PCM updates the Fuel Trim data in the Failure Records.
CONDITIONS FOR CLEARING THE MIL/DTC
The PCM turns the MIL OFF after three consecutive ignition cycles that the diagnostic runs and does not fail within the same conditions that the DTC last failed
CIRCUIT DESCRIPTION
The PCM controls a Closed Loop air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. The PCM monitors the heated oxygen sensor signal voltage and adjusts the fuel delivery based on the signal voltage while in Closed Loop. A change made to the fuel delivery changes the Long and Short Term Fuel Trim values. The Short Term Fuel Trim values change rapidly in response to the HO2S signal voltages. These changes fine tune the engine fueling. The Long Term Fuel Trim values change in response to trends in Short Term Fuel Trim. The Long Term Fuel Trim makes coarse adjustments to fueling in order to re-center and restore control to Short Term Fuel Trim. You can use a scan tool in order to monitor the Short and Long Term Fuel Trim. The ideal fuel trim values are around 0 percent . A positive Fuel Trim value indicates that the PCM is adding fuel in order to compensate for a lean condition. A negative Fuel Trim value indicates that the PCM is reducing the amount of fuel in order to compensate for a rich condition. If the PCM detects an excessively Rich or Lean condition, the PCM sets a DTC. The long term fuel trim diagnostic parameter is an average of several of the long term speed load learn cells which the PCM selects based on the engine speed and the engine load.
CONDITIONS FOR RUNNING THE DTC
DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0200, P0300, P0335, P0336, P0351-P0358, P0405, P0410, P0412, P0418, P0443, P0500, P0502, P0503, P1258, P1404, P1415, P1416 not set.
The engine coolant temperature is between 50°C (122°F) and 115°C (239°F).
The barometric pressure is more than 74 kPa.
The mass air flow is between 5.0 g/s and 90 g/s.
The manifold absolute pressure is between 26 kPa and 90 kPa.
The intake air temperature is between -20°C (-4°F) and 90°C (194°F).
The engine speed is between400 RPM and 3,000 RPM.
The TP sensor angle is less than 90 percent.
The vehicle speed is less than 137 km/h (85 mph).
CONDITIONS FOR SETTING THE DTC
The average Long Term Fuel Trim cell values are below a predetermined threshold.
All the above conditions are present for 40 seconds.
ACTION TAKEN WHEN THE DTC SETS
The PCM illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails, if the diagnostic fails under the same conditions (load, RPM, temperature, etc.) as the previous ignition cycle that the test ran and failed.
The first time the diagnostic fails, the PCM records the operating conditions in Failure Records.
The second consecutive ignition cycle that this diagnostic fails [under the same conditions (load, RPM, temperature, etc.) as the previous ignition cycle that the test ran and failed], the PCM stores this information in Freeze Frame. The PCM copies any data previously stored in Freeze Frame and copies the data into the Failure Records. The PCM then overwrites the Freeze Frame. The only exception to this is if a Misfire DTC was already recorded in Freeze Frame. In this case, the Misfire data stays in Freeze Frame and the PCM updates the Fuel Trim data in the Failure Records.
CONDITIONS FOR CLEARING THE MIL/DTC
The PCM turns the MIL OFF after three consecutive ignition cycles that the diagnostic runs and does not fail within the same conditions that the DTC last failed
