Refer to Engine Controls Schematic
Engine Data Sensors -- A/C Refrig Press, TP, MAP, ECT, IAT
.
Circuit Description
The throttle position (TP) sensor circuit provides a voltage signal that changes relative to the throttle blade angle. The signal voltage will vary from less than 1.0 volt at closed throttle to more than 4.0 volts at wide open throttle (WOT).
When the manifold absolute pressure (MAP) reading is less than 50 kPa, the diagnostic tests for a skewed high TP sensor. When the MAP reading is more than 70 kPa, the diagnostic tests for a skewed low TP sensor. If the powertrain control module (PCM) detects an out of range condition, DTC P0121 will set. The diagnostic will not run when MAP is between 50 kPa and 70 kPa.
Conditions for Running the DTC
| • | There are no active TP sensor circuit or manifold absolute pressure (MAP) sensor diagnostic trouble codes (DTCs). |
| • | The engine is running for more than 2 minutes |
| • | The ECT sensor temperature is more than 75°C (167°F). |
| • | The MAP reading is less than 50 kPa for a TP sensor that is skewed high. |
| • | The MAP reading is more than 70 kPa for a TP sensor that is skewed low. |
| • | The MAP is steady for 5 seconds or more. |
Conditions for Setting the DTC
| • | The TP sensor reading is more than the predicted value when the MAP is less than 50 kPa. |
| • | The TP sensor reading is less than the predicted value when the MAP is more than 70 kPa. |
| • | The above conditions are present for 10 seconds. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed. |
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using a scan tool. |
Diagnostic Aids
Inspect for the following conditions:
| • | A stuck or skewed MAP signal or a faulty MAP sensor. |
| • | A skewed MAP signal may cause the PCM to incorrectly determine the TP sensor is out of range. Test for an unusually low or high MAP reading. This condition can cause DTC P0121 to set. Refer to Manifold Absolute Pressure Sensor Circuit Diagnosis |
Many situations may lead to an intermittent condition. Perform each inspection or test as directed.
Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.
| • | Loose terminal connection |
| - | Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| - | Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| • | Damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
| • | Inspect the powertrain control module (PCM) and the engine grounds for clean and secure connections. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
If the condition is determined to be intermittent, reviewing the Snapshot or Freeze Frame/Failure Records may be useful in determining when the DTC or condition was identified.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||
2 |
Important: If any other DTCs are set, diagnose the other DTCs first.
Does the TP angle increase steadily and evenly from closed throttle value to wide open throttle value?
| 0 % 100 % | Go to Diagnostic Aids | |||||
3 |
Does the scan tool indicate that the TP voltage parameter is near the specified value? | 0.0 V | ||||||
4 |
Does the scan tool indicate that the TP voltage parameter is at the specified value? | 5.0 V | ||||||
5 | Test the signal circuit of the TP sensor for a short to voltage. Refer to Wiring Repairs in Wiring Systems . Did you find and correct the condition? | -- | ||||||
6 | Test the 5 volt reference circuit of the TP sensor for high resistance or a faulty connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems . Did you find and correct the condition? | -- | ||||||
7 | Test the signal circuit of the TP sensor for high resistance or a faulty connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||
8 | Test the ground circuit of the TP sensor for high resistance or a faulty connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||
9 | Inspect for faulty connections at the harness connector of the TP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||
10 | Replace the TP sensor. Refer Throttle Position Sensor Replacement . Did you complete the replacement? | -- | -- | |||||
|
Important: Replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- | ||||||
12 |
Does the scan tool indicate DTC P0121 failed this ignition? | -- | System OK |
