P0121
DTC P0121-P0123, P0222, P0223, or P2135
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC P0121
-
Throttle Position Sensor 1 Performance
DTC P0122
-
Throttle Position Sensor 1 Circuit Low Voltage
DTC P0123
-
Throttle Position Sensor 1 Circuit High Voltage
DTC P0222
-
Throttle Position Sensor 2 Circuit Low Voltage
DTC P0223
-
Throttle Position Sensor 2 Circuit High Voltage
DTC P2135
-
Throttle Position Sensors 1-2 Not Plausible
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The throttle body assembly contains 2 throttle position sensors. The throttle position sensors are mounted to the throttle body assembly and are not serviceable. The throttle position sensors provide a signal voltage that changes relative to throttle blade angle. The engine control module (ECM) supplies the throttle position sensors with a common 5 V reference circuit, a common low reference circuit, and 2 independent signal circuits.
The throttle position sensors have opposite functionality. Throttle position sensor 1 signal voltage decreases and throttle position sensor 2 signal voltage increases as the accelerator pedal increases to wide open throttle (WOT).
Conditions for Running the DTC
P0121
* DTCs P0096, P0097, P0098, P0102, P0103, P0107, P0108, P0111, P0112, P0113, P0116, P0117, P0118, P0119, P0128, P0236, P0237, P0238, P0335, P0336, P2227 - P2229 or P2230 are not set.
* The engine speed is between 400-6 000 RPM.
* The engine coolant temperature (ECT) is between -7 to +125°C (19.4-+257°F).
* The intake air temperature (IAT) is between -20 to +100°C (-4 to +212°F).
* DTC P0121 run continuously when the above conditions are met.
P0122, P0123, P0222, P0223
* DTC P06A3 is not set.
* The run/crank or powertrain relay voltage is greater than 6.41 V.
* The ignition is ON, or the engine is running.
* DTC P0122, P0123, P0222 or P0223 runs continuously when the above conditions are met.
P2135
* DTCs P0122, P0123, P0222, P0223, or P06A3 are not set.
* The run/crank or powertrain relay voltage is greater than 6.41 V.
* The ignition is ON, or the engine is running.
* DTC P2135 runs continuously when the above conditions are met.
Conditions for Setting the DTC
P0121
The ECM detects that the throttle position sensor 1 voltage is stuck in range for greater than 1 s.
P0122
The ECM detects that the throttle position sensor 1 voltage is less than 0.33 V for greater than 0.4 s.
P0123
The ECM detects that the throttle position sensor 1 voltage is greater than 4.75 V for greater than 0.4 s.
P0222
The ECM detects that the throttle position sensor 2 voltage is less than 0.25 V for greater than 0.4 s.
P0223
The ECM detects that the throttle position sensor 1 voltage is greater than 4.59 V for greater than 0.4 s.
P2135
The difference between the throttle position sensor 1 and throttle position sensor 2 exceeds a predetermined value for greater than 2 s.
Action Taken When the DTC Sets
P0121
* DTCs P0121 is a Type B DTC.
* The control module commands the throttle actuator control (TAC) system to operate in the Reduced Engine Power mode.
P0122, P0123, P0222, P0223 or P2135
* DTCs P0122, P0123, P0222, P0223 and P2135 are Type A DTCs.
* The control module commands the throttle actuator control (TAC) system to operate in the Reduced Engine Power mode.
Conditions for Clearing the DTC
* DTC P0121 is a Type B DTC.
* DTCs P0122, P0123, P0222, P0223 and P2135 are Type A DTCs.
Diagnostic Aids
A high resistance condition on the throttle position sensor or throttle actuator control circuits could cause a DTC to set.
Reference Information
Schematic Reference
Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Throttle Actuator Control (TAC) System Description Throttle Actuator Control (TAC) System Description
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON, observe the DTC information with a scan tool. Verify DTC P06A3 is not set.
• If the DTC is set, refer to DTC P0641, P0651, P0697, or P06A3 (ECM) Powertrain Management (ECM).
2. Verify the scan tool Throttle Body Idle Air Flow Compensation parameter is less than 90%.
• If 90% or greater, refer to Throttle Body Inspection and Cleaning Procedures.
3. Verify the scan tool Throttle Position Sensor 1 and Throttle Position Sensor 2 voltage parameters are between 1.0-4.0 V.
• Refer to Circuit/System Testing.
4. Verify the Throttle Position Sensors 1 and 2 Agree/Disagree parameter displays Agree while performing the Throttle Sweep Test with a scan tool.
• Test or replace the Q38 Throttle Body.
5. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. or operate the vehicle within the conditions from the freeze frame/failure records data.
6. Observe the DTC Information with a scan tool. DTCs P0121, P0122, P0123, P0221, P0222 and P2135 should not set.
• If the DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
Circuit/System Testing
Note:
You must perform the circuit/system verification before proceeding with circuit/system testing.
1. Ignition OFF, disconnect the harness connector at the Q38 Throttle Body. Allow sufficient time for the K20 Engine Control Module to completely power down.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal C and ground.
• If greater than 5 ohms, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
3. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal E and ground.
• If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
• If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.
4. Test for less than 1 V between the Throttle Position Sensor 1 signal circuit terminal D and ground.
• If greater than specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.
5. Test for 4.8-5.2 V between the Throttle Position Sensor 2 signal circuit terminal F and ground.
• If less than specified range, test the signal circuit for a short to ground, or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
• If greater than specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.
6. Install a 3 A fused jumper wire between Throttle Position Sensor 1 signal circuit terminal D and the 5 V reference circuit terminal E. Verify the scan tool Throttle Position Sensor 1 voltage parameter is greater than 4.8 V.
• If less than the specified range, test the signal circuit for a short to ground, or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
7. If all circuits test normal, replace the Q38 Throttle Body.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Throttle Body Assembly Replacement Removal and Replacement
* Control Module References Control Module References for ECM replacement, programming and setup