2010 Cadillac Truck Escalade/ESV RWD V8-6.2L Page 1841
Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC P0171
- Fuel Trim System Lean Bank 1
DTC P0172
- Fuel Trim System Rich Bank 1
DTC P0174
- Fuel Trim System Lean Bank 2
DTC P0175
- Fuel Trim System Rich Bank 2
Circuit/System Description
The engine control module (ECM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel
economy, and emission control. Fuel delivery is controlled differently during Open Loop and Closed Loop (CL). During Open Loop, the ECM
determines fuel delivery based on sensor signals without heated oxygen sensor (HO2S) input. During CL, the ECM adds HO2S inputs and level of
purge to calculate the short and long term fuel trim (FT) adjustments. If the HO2S indicates a lean condition, the fuel trim values will be above 0 %.
If the HO2S indicates a rich condition, the FT values will be below 0 %. The short term FT values change rapidly in response to the HO2S voltage
signals. The long term FT makes coarse adjustments in order to maintain an optimum air/fuel ratio. A block of cells contain information arranged in
combinations of engine RPM and engine load for a full range of vehicle operating conditions. The long term FT diagnostic is based on an average
of cells currently being used. The ECM selects the cells based on the engine speed and load. The FT diagnostic will conduct a test to determine if a
rich failure actually exists or if excessive vapor from the evaporative emission (EVAP) canister is causing a rich condition.
If the ECM detects an excessively lean condition, DTC P0171 or P0174 sets. If the ECM detects an excessively rich condition, DTC P0172 or
P0175 sets.
Conditions for Running the DTC
* DTCs P0030, P0036, P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0117, P0118, P0120, P0121, P0128, P0130, P0131, P0132,
P0133, P0134, P0135, P0136, P0137, P0138, P0140, P0141, P0201-P0208, P0220, P0300, P0301-P0304, P0442, P0443, P0446, P0449,
P0452, P0453, P0455, P0496, P1106, P1107, P1114, P1115, P1133, P1516, P2101, P2119, P2120, P2125, P2135, P2138, P2176 are not set.
* The engine is in Closed Loop status.
* The engine coolant temperature (ECT) is between -40 and +150掳C (-40 and +302掳F).
* The intake air temperature (IAT) is between -20 and +150掳C (-4 and +302掳F).
* The manifold absolute pressure (MAP) is between 10-255 kPa (1.45-37 psi).
* The vehicle speed is less than 134 km/h (83 mph).
* The engine speed is between 375-7,000 RPM.
* The mass air flow (MAF) is between 1-510 g/s.
* The barometric pressure (BARO) is more than 70 kPa (10.2 psi).
* The fuel level is more than 10 %.
* This diagnostic runs continuously when the above conditions have been met.
Conditions for Setting the DTC
* The average long term FT weighted average value is more or less than a calibrated value.
* The above condition is present for approximately 3 min after the Conditions for Running the DTC have been met.
Action Taken When the DTC Sets
The ECM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the ECM stores this information in the
Failure Records. If the diagnostic reports a failure on the second ignition cycle the ECM records the operating conditions at the time of the failure.
The ECM writes the operating conditions to the Freeze Frame and updates the Failure Records. The ECM illuminates the malfunction indicator
lamp (MIL) when one of the following occur:
* The ECM detects the same fuel trim failure during 2 consecutive trips.
* The ECM detects any fuel trim failure during any subsequent trip if the conditions at the time of failure meet the following criteria:
- The engine load is within 20 % of the previous test that failed.
- The engine speed is within 375 RPM of the previous test that failed.
- The engine coolant temperature is in the same range of the previous test that failed.
Conditions for Clearing the MIL/DTC
* The ECM turns OFF the malfunction indicator lamp (MIL) at the beginning of the fourth ignition cycle, after 3 ignition cycles that the
diagnostic runs and does not fail.
