Engine Controls - 4.8l, 5.3l & 6.0l (p1133 to u0107) Chevrolet Cab & Chassis Silverado 3500

Circuit Description

Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The powertrain control module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and closed loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream. This diagnostic will only run once per ignition cycle. The PCM monitors the number of rich to lean and lean to rich transitions. If the PCM detects that the number of transitions were less than a specified value, DTC P1133 sets for HO2S bank 1 sensor 1 or DTC P1153 sets for HO2S bank 2 sensor 1.

DTC Descriptors

This diagnostic procedure supports the following DTCs

1. DTC P1133 HO2S Insufficient Switching Bank 1 Sensor 1
2. DTC P1153 HO2S Insufficient Switching Bank 2 Sensor 1

Conditions for Running the DTC

1. DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0128, P0131, P0132, P0134, P0135, P0151, P0152, P0154, P0155, P0169, P0178, P0179, P0200, P0220, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1516, P2101, P2108, P2135, U0107 are not set.
2. The ECT Sensor parameter is greater than 60°C (140°F).
3. The EVAP Purge Solenoid Command parameter is greater than 1 percent.
4. The Fuel Alcohol content parameter is less than 90 percent.
5. The MAF Sensor parameter is between 20-55 g/s.
6. The Engine Speed parameter is between 1,200-3,000 RPM.
7. The TP Indicated Angle parameter is 5 percent more than the value observed at idle.
8. The Loop Status parameter is closed.
9. The Ignition 1 Signal parameter is between 10-18 volts.
10. The Fuel Tank Level Remaining parameter is greater than 10 percent.
11. The Engine Run Time parameter is more than 160 seconds.
12. The above conditions are met for 1 second.
13. This diagnostic runs one time per drive cycle once the above conditions are met.

Conditions for Setting the DTC

The PCM detects that the affected HO2S lean-to-rich or rich-to-lean transitions are less than a calibrated value for 100 seconds.

Action Taken When the DTC Sets

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Test Description

The number below refers to the step number on the diagnostic table.

1. 2: If the voltage is varying above and below the specified value, the condition is not present.

DTC P1133 or P1153

Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The powertrain control module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and closed loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream. This diagnostic will only run once per ignition cycle. The PCM monitors the rich-to-lean and lean-to-rich transition time. A transition is defined as, the HO2S voltage changes from greater than 625 mV to less than 250 mV or from less than 250 mV to greater than 625 mV. If the PCM detects that the difference between the rich-to-lean average transition time and lean-to-rich average transition time is greater than a specified value, DTC P1134 sets for HO2S bank 1 sensor 1, or DTC P1154 sets for HO2S bank 2 sensor 1.

This diagnostic procedure supports the following DTCs

1. DTC P1134 HO2S Transition Time Ratio Bank 1 Sensor 1
2. DTC P1154 HO2S Transition Time Ratio Bank 2 Sensor 1

1. DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0128, P0131, P0132, P0134, P0135, P0151, P0152, P0154, P0155, P0169, P0178, P0179, P0200, P0220, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1516, P2101, P2108, P2135, U0107 are not set.
2. The ECT Sensor parameter is more than 60°C (140°F).
3. The EVAP Purge Solenoid Command parameter is more than 1 percent.
4. The MAF Sensor parameter is between 20-55 g/s.
5. The Engine Speed parameter is between 1,200-3,000 RPM.
6. The TP Indicated Angle parameter is 5 percent more than the value observed at idle.
7. The Loop Status parameter is closed.
8. The Ignition 1 Signal parameter is between 10-18 volts.
9. The Fuel Alcohol content parameter is less than 90 percent.
10. The Fuel Tank Level Remaining parameter is more than 10 percent.
11. The Engine Run Time parameter is more than 160 seconds.
12. The above conditions are met for 1 second.
13. This diagnostic runs one time per drive cycle once the above conditions are met.

The PCM detects that the difference between the HO2S rich-to-lean average transition time and the lean-to-rich average transition time is more than a calibrated value for 100 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The number below refers to the step number on the diagnostic table.

1. 2: If the voltage is varying above and below the specified value, the condition is not present.

DTC P1134 or P1154

System Description

The powertrain control module (PCM) detects engine misfire events by monitoring variations in the crankshaft rotation speed. Wheel speed changes caused by rough road conditions can cause changes in crankshaft speed. By monitoring the wheel speed sensors, the antilock brake system (ABS) can determine if the vehicle is operating on a rough road. If the ABS is detecting a rough road condition severe enough to effect misfire detection, a rough road signal is sent to the PCM on the serial data circuit. If DTC P0300 is set with the malfunction indicator lamp (MIL) illuminated, and the rough road information is not available due to an ABS malfunction, DTC P1380 will set.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC P1380 Misfire Detected - Rough Road Data Not Available

1. The vehicle speed is greater than 8 km/h (5 mph).
2. The engine load is less than 60 percent.
3. The engine misfire is detected and DTC P0300 is set with the MIL illuminated.
4. The engine speed is less than 7,000 RPM.
5. DTC P1380 runs continuously when the above conditions are met.

An ABS malfunction exists for more than 45 seconds, preventing the PCM from receiving rough road detection data.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
3. The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

DTC P1380

The powertrain control module (PCM) detects engine misfire events by monitoring variations in the crankshaft rotation speed. Wheel speed changes caused by rough road conditions can cause changes in crankshaft speed. By monitoring the wheel speed sensors, the antilock brake system (ABS) can determine if the vehicle is operating on a rough road. If the ABS is detecting a rough road condition severe enough to effect misfire detection, a rough road signal is sent to the PCM on the serial data circuit. If DTC P0300 is set with the malfunction indicator lamp (MIL) illuminated and there is no communication with the brake control module, DTC P1381 will set.

This diagnostic procedure supports the following DTC

DTC P1381 Misfire Detected - No Communication With Brake Control Module

1. The vehicle speed is above 8 km/h (5 mph).
2. The engine speed is below 7,000 RPM.
3. The engine load is less than 60 percent.
4. Engine misfire is detected and DTC P0300 is set with the MIL illuminated.
5. DTC P1381 runs continuously when the above conditions are met.

The PCM cannot communicate with the brake control module for more than 45 seconds.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
3. The driver information center, if equipped, may display a message.

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

DTC P1381

The predicted throttle position (TP) is compared to the actual throttle position. The two values should be within a calibrated range of each other. Both the powertrain control module (PCM) and the throttle actuator control (TAC) module redundantly monitor the predicted and actual throttle position. DTC P1516 sets if the PCM detects an out of range condition between the predicted and the actual throttle position.

This diagnostic procedure supports the following DTC

DTC P1516 Throttle Actuator Control (TAC) Module Throttle Actuator Position Performance

1. DTC P2108 or U0107 is not set.
2. The ignition switch is in the Crank or Run position.
3. The ignition voltage is more than 5.23 volts.
4. The TAC system is not in the battery saver mode.
5. DTC P1516 runs continuously once the above conditions are met.

1. The TAC module detects that the predicted and the actual throttle positions are not within a calibrated range of each other. OR
2. The PCM or the TAC module cannot determine the throttle position. OR
3. Both of the TP sensors are out of range.
4. The PCM detects one of the above conditions are present for more than 0.003 second.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine OFF.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

1. Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
2. Verify that the starting and charging systems are operating properly. Low system voltage can cause this DTC to set.
3. When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing an individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
4. For an intermittent, refer to «Testing for Intermittent Conditions and Poor Connections»(ref-197325-S02683201702005101100000) .

The numbers below refer to the step numbers on the diagnostic table.

1. 7: If the TP indicated angle does not follow the movement of the throttle blade and no TP sensor DTCs are set, there is a mechanical condition with the throttle shaft or the TP sensor.
2. 18: Locating and repairing an individual condition may correct more than one DTC.

DTC P1516

The commanded throttle position (TP), based on accelerator pedal position (APP) and possibly other limiting factors, is compared to the actual TP. The two values should be within a calibrated range of each other. Both the powertrain control module (PCM) and the throttle actuator control (TAC) module redundantly monitor the commanded and actual TP. DTC P2101 sets if the PCM detects an out-of-range condition between the commanded and the actual throttle position.

This diagnostic procedure supports the following DTC

DTC P2101 Control Module Throttle Actuator Position Performance

1. DTCs P0068, P0601, P0602, P0604, P0606, P1516, P2108, U0107 are not set.
2. DTCs P0120 and P0220 are not active at the same time.
3. The engine is running. OR
4. The ignition voltage is more than 8.5 volts with the ignition ON.
5. The TAC system is not in the battery saver mode.
6. DTC P2101 runs continuously once the above conditions are met.

The PCM detects that the commanded and actual throttle positions are not within 6 percent of each other for more than 0.19 second.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine OFF.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Inspect for mechanical concerns or binding that may be temperature related. Components may not move freely in extreme heat or cold due to the presence of contaminants or ice formation.
2. Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
3. When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing an individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
4. For an intermittent, refer to «Testing for Intermittent Conditions and Poor Connections»(ref-197325-S02683201702005101100000) .

The numbers below refer to the step numbers on the diagnostic table.

1. 4: If the TP indicated angle does not follow the movement of the throttle blade and no TP sensor DTCs are set, there is a mechanical condition with the throttle shaft or the TP sensor.
2. 15: Locating and repairing an individual condition may correct more than 1 DTC.

DTC P2101

The throttle actuator control (TAC) module contains data which is essential for proper TAC system operation. The TAC module continuously tests the integrity of this data. When the TAC module is unable to write or read data to and from random access memory (RAM), or the TAC module is unable to correctly read data from the flash memory or an internal TAC module processor fault is detected, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P2108 Throttle Actuator Control (TAC) Module Performance

1. DTC U0107 is not set.
2. The ignition switch is in the Crank or Run position.
3. The ignition voltage is greater than 5.23 volts.
4. The communication between the TAC module and the powertrain control module (PCM) must be valid.
5. DTC P2108 runs continuously once the above conditions are met.

The TAC module determines that an internal data test did not pass for between 0.8-60 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine OFF.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Verify that the starting and charging systems are operating properly. Low system voltage can cause this DTC to set.
2. Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
3. When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing an individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.

The number below refers to the step number on the diagnostic table.

1. 4: Locating and repairing an individual condition may correct more than one DTC.

DTC P2108

The accelerator pedal position (APP) sensor 1 is a potentiometer type sensor with the following three circuits

1. A 5-volt reference circuit
2. A low reference circuit
3. A signal circuit

The control module provides the APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensor then provides the control module a signal voltage proportional to pedal movement. The APP sensor 1 signal voltage is low at rest and increases as the pedal is depressed. This DTC incorporates the following diagnostic tests

1. The APP sensor 1 signal circuit voltage out of range
2. The accelerator pedal minimum position for the APP sensor 1 out of range
3. The 5-volt reference of the APP sensor 1 voltage out of range

If the PCM detects one or more of the APP sensor 1 tests are out of range, DTC P2120 sets.

This diagnostic procedure supports the following DTC

DTC P2120 Accelerator Pedal Position (APP) Sensor 1 Circuit

1. DTCs P0601, P0602, P0606, P2108, U0107 are not set.
2. The ignition switch is in the Crank or Run position.
3. The ignition voltage is more than 5.23 volts.
4. DTC P2120 runs continuously once the above conditions are met.

1. The PCM detects that the APP sensor 1 signal voltage is less than 0.24 volts or more than 4.49 volts. OR
2. The accelerator pedal minimum position for the APP sensor 1 is less than 0.24 volts. OR
3. The 5-volt reference voltage is less than 4.54 volts or more than 5.21 volts.
4. One of the above conditions is present for more than 0.1 second.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. If one or more APP sensor DTCs are set, the following occurs: The control module commands Reduced Engine Power mode. The APP indicated angle is limited to a predetermined value to limit the amount of throttle control. OR The APP indicated angle is limited to 0 percent. The control module only allows the engine to idle. The message center displays Reduced Engine Power.

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

1. Inspect the throttle actuator control (TAC) module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
2. When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
3. For an intermittent, refer to «Testing for Intermittent Conditions and Poor Connections»(ref-197325-S02683201702005101100000) .

The numbers below refer to the step numbers on the diagnostic table.

1. 12: This test isolates whether the short is to another TAC system circuit in the harness or within the TAC module.
2. 26: When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.

DTC P2120

The accelerator pedal position (APP) sensor 1 and APP sensor 2 are potentiometer type sensors, each with the following circuits

1. A 5-volt reference circuit
2. A low reference circuit
3. A signal circuit

The control module provides the APP sensors a 5-volt reference circuit and a low reference circuit. The APP sensors then provide the control module signal voltages proportional to pedal movement. The APP sensor 1 signal voltage is low at rest and increases as the pedal is depressed. The APP sensor 2 signal voltage is also low at rest and increases as the pedal is depressed.

This DTC incorporates the following diagnostic tests

1. The APP sensor 1 to APP sensor 2 correlation
2. The accelerator pedal minimum position correlation between the APP sensor 1 and APP sensor 2
3. The APP sensor 1 signal shorted to a 5-volt reference, ground, or the APP sensor 2 signal

If the PCM detects one or more of the APP sensor 1 tests are out of range, DTC P2121 sets.

This diagnostic procedure supports the following DTC

DTC P2121 Accelerator Pedal Position (APP) Sensor 1 Performance

1. DTCs P0606, P2108, or U0107 are not set.
2. The ignition switch is in the Crank or Run position.
3. The ignition voltage is more than 5.23 volts.
4. DTC P2121 runs continuously once the above conditions are met.

1. The PCM detects that the APP sensor 1 disagrees with APP sensor 2 by more than 10.5 percent.
2. The above condition is present for more than 0.14 second.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. If one or more APP sensor DTCs are set for a single APP sensor, the following occurs: The control module commands Reduced Engine Power mode. The APP indicated angle is limited to a predetermined value to limit the amount of throttle control. The APP indicated angle is limited to 0 percent. The control module only allows the engine to idle. The message center displays Reduced Engine Power.

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

1. Inspect the throttle actuator control (TAC) module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
2. When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
3. For an intermittent, refer to «Testing for Intermittent Conditions and Poor Connections»(ref-197325-S02683201702005101100000) .

The numbers below refer to the steps numbers in the diagnostic table.

1. 2: This step determines if a communication condition exists.
2. 5: This step isolates an internal APP sensor failure. The condition may only occur at a certain accelerator pedal position. Monitoring the APP angles for sensor 2 and sensor 3 is an accurate way of verifying the actual position of the pedal. The APP angles for all 3 sensors should be within a few percent of each other. If the pedal is at rest, the APP angle for all 3 sensors should be 0 percent. If the pedal is fully depressed, all APP angles should be 100 percent.
3. 6: The APP sensor 1 shares a common 5-volt reference circuit with the throttle position (TP) sensor 1. Monitoring the TP sensor 1 voltage aids in diagnosing the APP sensor 5-volt reference and low reference circuits.
4. 9: With the TAC module still connected, this test will help determine a short to the signal circuit either within the TAC module or the wiring.
5. 10: This step determines whether the TAC module or a shorted circuit is causing the condition.
6. 19: When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.

DTC P2121

The accelerator pedal position (APP) sensor 2 is a potentiometer type sensor with the following circuits

1. A 5-volt reference circuit
2. A low reference circuit
3. A signal circuit

The control module provides the APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensor then provides the control module a signal voltage proportional to pedal movement. The APP sensor 1 signal voltage is low at rest and increases as the pedal is depressed.

This DTC incorporates the following diagnostic tests

1. The APP sensor 2 signal circuit voltage out of range
2. The accelerator pedal minimum position for the APP sensor 2 out of range
3. The 5-volt reference of the APP sensor 2 tests out of range

If the powertrain control module (PCM) detects one or more of the APP sensor 2 tests are out of range, DTC P2125 sets.

This diagnostic procedure supports the following DTC

DTC P2125 Accelerator Pedal Position (APP) Sensor 2 Circuit

1. DTCs P0601, P0602, P0606, P2108, U0107 are not set.
2. The ignition switch is in the Crank or Run position.
3. The ignition voltage is more than 5.23 volts.
4. DTC P2125 runs continuously once the above conditions are met.

1. The PCM detects that the APP sensor 2 signal voltage is less than 0.24 volt or more than 4.49 volts. OR
2. The accelerator pedal minimum position for the APP sensor 2 is less than 0.24 volts. OR
3. The 5-volt reference voltage is less than 4.54 volts or more than 5.21 volts.
4. One of the above conditions is present for more than 0.14 second.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. If one or more APP sensor DTCs are set, the following occurs: The control module commands Reduced Engine Power mode. The APP indicated angle is limited to a predetermined value to limit the amount of throttle control. OR The APP indicated angle is limited to 0 percent. The control module only allows the engine to idle. The message center displays Reduced Engine Power.

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

1. Inspect the throttle actuator control (TAC) module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
2. When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
3. For an intermittent, refer to «Testing for Intermittent Conditions and Poor Connections»(ref-197325-S02683201702005101100000) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: The throttle position (TP) sensor 2 and the APP sensor 2 share a common 5-volt reference source. Diagnose DTC P0220 first if that DTC is also set.
2. 18: This test determines whether or not the TAC module can recognize a change in signal voltage.
3. 19: There are 2 separate 5-volt reference sources within the TAC module. The TP sensor 1 and the APP sensor 1 share one 5-volt reference source. The TP sensor 2 and the APP sensor 2 share another common 5-volt reference source. This test determines whether the signal circuit is shorted to any one of the 5-volt reference circuits. If a short exists, the corresponding sensor voltage will be pulled low.
4. 20: The previous step found the signal circuit and a 5-volt reference circuit shorted together. This test isolates whether the short is in the harness or within the TAC module.
5. 26: When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.

DTC P2125

The throttle position (TP) sensor incorporates two ratio metric TP sensors into one housing. TP sensor 1 and TP sensor 2 each have a 5-volt reference circuit supplied by the throttle actuator control (TAC) module. The TAC module supplies each TP sensor with a low reference circuit. Each TP sensor supplies the TAC module with a signal voltage that is proportional to the throttle blade position. Both of the TP signal voltages increase as the throttle blade is opened. The TP sensor 1 and the accelerator pedal position (APP) sensor 1 share a 5-volt reference circuit that is bussed within the TAC module. The TP sensor 2 and the APP sensor 2 share a 5-volt reference circuit that is also bussed within the TAC module. When this DTC sets, the Reduced Engine Power indicator will be displayed.

This DTC incorporates the following diagnostic tests

1. The TP sensor 1 and the TP sensor 2 correlation
2. The throttle blade minimum position correlation between the TP sensor 1 and the TP sensor 2
3. The TP sensor 1 signal shorted to a 5-volt reference, a ground, or the TP sensor 2 signal circuit

If the powertrain control module (PCM) detects one or more of the TP sensor 1 tests are out of range, DTC P2135 sets.

This diagnostic procedure supports the following DTC

DTC P2135 Throttle Position (TP) Sensor 1-2 Correlation

1. DTCs P2108 or U0107 are not set.
2. The ignition switch is in the Crank or Run position.
3. The ignition voltage is more than 5.23 volts.
4. The TP sensor 1 to TP sensor 2 correlation test runs continuously.
5. The throttle blade minimum position correlation test runs once after the ignition is turned ON.
6. The TP sensor 1 signal circuit short test runs continuously.

The TP sensor 1 to TP sensor 2 correlation error is more than 6 percent for more than 0.14 second.

OR

The PCM detects a short on the TP sensor 1 signal circuit for more than 0.10 second.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine OFF.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
2. When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
3. If this DTC is determined to be intermittent, refer to «Testing for Intermittent Conditions and Poor Connections»(ref-197325-S02683201702005101100000) .

The number below refers to the step number on the diagnostic table.

1. 21: When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.

DTC P2135

The secondary fuel pump is located in the rear fuel tank. The secondary fuel pump is powered by a secondary fuel pump relay. Fuel is transferred from the rear fuel tank to the front fuel tank in order to ensure all of the usable fuel volume is available to the primary fuel pump. The secondary fuel pump relay supply voltage is received from the primary fuel pump relay when the primary fuel pump is energized. This DTC sets when the powertrain control module (PCM) commands the secondary fuel pump ON and a predetermined change in both the front and rear fuel level sensors does not occur.

This diagnostic procedure supports the following DTC

DTC P2636 Fuel Transfer Pump Flow Insufficient

1. DTCs P0461, P0462, P0463, P2066, P2067, P2068 are not set.
2. The vehicle speed is 0 km/h (0 mph).
3. The engine has been idling for more than 2 minutes and 20 seconds.
4. The primary fuel level is less than 60 L (15.8 gal).
5. The secondary fuel level is more than 3 L (2.6 gal).

The PCM does not detect a change of 4 L (1.06 gal), in both the primary and the secondary fuel level sensors, with the secondary pump commanded ON for 120 seconds.

1. The PCM stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.
4. The driver information center, if equipped, may display a message.

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step tests the supply voltage circuit of the secondary fuel pump relay. The test lamp should illuminate as the primary fuel pump is commanded ON.
2. 4: This step verifies the secondary fuel pump operation. Listen for an audible sound as the secondary fuel pump relay harness connector is jumpered.
3. 5: This step verifies that there is adequate fuel in the rear fuel tank. The rear fuel tank sensor voltage must be above 1 volt in order to continue.
4. 7: This step tests the secondary fuel pumps ability to transfer fuel. The rear fuel level sensor voltage should decrease while the secondary fuel pump is ON.
5. 8: This step tests for a short to ground on the control circuit of the secondary fuel pump relay. If the test lamp illuminates, a short to ground is indicated.
6. 9: This step tests for a short to voltage on the control circuit of the secondary fuel pump relay. If the test lamp illuminates, a short to voltage is indicated.
7. 10: This step verifies the secondary fuel pump relay operation. An audible click should be heard as the secondary fuel pump relay control circuit is grounded. The secondary fuel pump should turn ON as the fuel pump relay control circuit is grounded.

DTC P2636

Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The powertrain control module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and closed loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream.

The HO2S bank 1 sensor 2 and HO2S bank 2 sensor 2 are used for catalyst monitoring. This diagnostic runs once per ignition cycle. This diagnostic consists of two tests, a passive test and an intrusive test. During the passive test, if the HO2S bank 1 sensor 2 or HO2S bank 2 sensor 2 voltage transitions less than 349 mV and greater than 710 mV, the DTC will pass for this ignition cycle. If the DTC does not pass during the passive test, the intrusive test will begin. During the intrusive test, the control module will force the air-to-fuel ratio rich and/or lean. The control module then waits for a predicted response from the HO2S. If the HO2S voltage transitions less than 349 mV or greater than 710 mV, the DTC will pass for this ignition cycle. If the control module does not receive the expected response from the HO2S, DTC P2A01 will set for HO2S bank 1 sensor 2 or DTC P2A04 will set for HO2S bank 2 sensor 2.

This diagnostic procedure supports the following DTCs

1. DTC P2A01 HO2S Performance Bank 1 Sensor 2
2. DTC P2A04 HO2S Performance Bank 2 Sensor 2

DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0128, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0151, P0152, P0153, P0154, P0155, P0157, P0158, P0160, P0161, P0200, P0442, P0443, P0446, P0449, P0455, P0496, P1133, P1134, P1153, P1154 are not set.

Passive Test

1. The engine is running.
2. The Engine Run Time parameter is less than 13.5 minutes.
3. The above conditions are met for 2 seconds.
4. This diagnostic runs one time per drive cycle once the above conditions are met.

Intrusive Test

1. The Engine Run Time parameter is more than 13.5 minutes.
2. The Ignition 1 Signal parameter is between 10-18 volts.
3. The Engine Speed parameter is between 900-5,000 RPM.
4. The MAF Sensor parameter is between 5-100 g/s.
5. The Vehicle Speed parameter is between 24-131 km/h (15-82 mph).
6. The Short Term FT Bank 1 and Bank 2 parameter is between -4 and +4 percent.
7. The maximum number of intrusive attempts is less than 100.
8. The above conditions are met for 3 seconds.
9. This diagnostic runs one time per drive cycle once the above conditions are met.

1. The PCM detects that the HO2S bank 1 sensor 2 or HO2S bank 2 sensor 2 did not transition less than 349 mV and greater than 710 mV during the passive test.
2. One of the following tests fail: Lean Intrusive Test The PCM detects that the HO2S bank 1 sensor 2 or HO2S bank 2 sensor 2 is greater than 349 mV for 60 seconds. The HO2S bank 1 sensor 1 and HO2S bank 2 sensor 1 is less than 300 mV.

Rich Intrusive Test

1. The PCM detects that the HO2S bank 1 sensor 2 or HO2S bank 2 sensor 2 is less than 710 mV for 60 seconds.
2. The HO2S bank 1 sensor 1 and HO2S bank 2 sensor 1 is greater than 600 mV.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers on the diagnostic table.

1. 2: If the voltage does not change more than the specified value, the condition is present.

DTC P2A01 or P2A04

The throttle actuator control (TAC) module and the powertrain control module (PCM) communicate via a dedicated serial data circuit. This serial data circuit is separate from any other serial data circuit on the vehicle. Accurate transmitting and receiving of serial data requires not only good circuit integrity, but also adequate system voltage. This diagnostic test monitors the accuracy of the serial data transmitted between the TAC module and the PCM. If the PCM detects a loss of data or invalid data, DTC U0107 sets.

This diagnostic procedure supports the following DTC

DTC U0107 Lost communication with Throttle Actuator Control (TAC) Module

1. The ignition switch is in the Run position.
2. The ignition voltage is more than 5.23 volts.
3. DTC U0107 runs continuously once the above conditions are met.

The PCM detects invalid or missing serial data messages for more than 0.83 second.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine OFF.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. DTC U0107 sets if the battery voltage is low. If the customer concern is slow cranking or no crank because battery voltage is low, ignore DTC U0107. Clear any DTCs from memory that may have set from the low battery voltage condition.
2. DTC U0107 sets when there is a short to B+ on the TAC module ground circuit. Inspect the fuses for the circuits that are in the TAC module harness, i.e. cruise, brake. An inspection of the fuses may lead you to the circuit that is shorted to the TAC module ground circuit.
3. DTC U0107 sets if the TAC module ignition feed circuit is shorted to a B+ supply circuit. The TAC module stays powered-up when the ignition switch is turned OFF. When the ignition switch is turned ON, the TAC module is powered-up before the PCM. DTC U0107 sets because no communication is detected by the TAC module from the PCM. Inspect related circuits for being shorted to a B+ supply circuit.
4. Inspect the TAC module power and ground circuits and the TAC module/PCM serial data circuits for intermittent connections.
5. Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
6. When the TAC module detects a problem within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing an individual condition may correct more than one DTC. Remember this if you review the stored information in Capture Info.
7. For an intermittent condition, refer to «Testing for Intermittent Conditions and Poor Connections»(ref-197325-S02683201702005101100000) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step determines if the ignition relay is supplying a voltage to the ETC fuse.
2. 5: Increasing the engine speed to 3,000 RPM aids in locating a shorted throttle actuator motor control circuit. Depending on the polarity of the throttle actuator motor transistors, this DTC may not set with a fault in the control circuits. The throttle actuator motor is a bi-directional DC motor. Raising the engine speed changes the polarity of the transistors in the throttle actuator motor. This occurs because one set of the transistors is low, 0 volts, and the other set is high, B+. Therefore, if one set of transistors is at a low voltage and the corresponding circuit is shorted low, DTC P1518 will not set. When the polarity of the transistors change, this DTC sets. If this DTC does not fail this ignition, continue to monitor this DTC status while moving related harnesses and connectors.
3. 29: Locating and repairing an individual condition may correct more than one DTC.

DTC U0107

See also:
• Engine Controls Schematics
• Engine Controls Connector End Views
• Powertrain Control Module (PCM) Connector End Views
• Scan Tool Data List
• Alcohol/Contaminants-in-Fuel Diagnosis (without Special Tool and E85)
• Oil Consumption Diagnosis
• Symptoms - Antilock Brake System
• DTC P0120
• DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681, P1683, or P2610
• DTC U0107