Circuit Description
The throttle position (TP) sensor circuit provides a voltage signal that changes relative to throttle blade angle. The TP sensor sends a voltage signal back to the engine control module (ECM) relative to the throttle plate opening. The voltage signal will vary from approximately 0.33 volts at closed throttle, to over 4.3 volts at wide open throttle (WOT).
The TP signal is used by the ECM for fuel control and for most of the ECM controlled outputs. The TP signal is one of the most important inputs used by the ECM for fuel control and most of the ECM controlled outputs. If the ECM detects a TP signal that is intermittently above the range of the TP sensor, DTC P1121 will be set.
Conditions for Setting the DTC
The TP sensor voltage indicates a throttle voltage intermittently greater than 4.9 volts.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The ECM will store conditions which were present when the DTC set as Failure Records data only. This information will not be stored as Freeze Frame data. |
| • | A history DTC is stored. |
Conditions for Clearing the MIL/DTC
| • | A history will clear after 40 consecutive warm-up cycles in which the diagnostic runs without a fault. |
| • | DTCs can be cleared by using the scan tool. |
| • | Disconnect the ECM battery feed for more than 10 seconds. |
Diagnostic Aids
Inspect for the following conditions:
| • | A poor connection at the ECM--Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and a poor terminal-to-wire connection. |
| • | A damaged harness--Inspect the wiring harness for damage. If the harness appears OK, observe the throttle position display on the scan tool while moving connectors and wiring harnesses related to the TP sensor. A change in the display will indicate the location of the fault. |
If DTC P1121 cannot be duplicated, reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Yes | No |
|---|---|---|---|
Perform an On-Board Diagnostic System Check. Was the check performed? | Go to Step 2 | ||
2 |
Is DTC P0123 also set? | Go to applicable DTC table | Go to Step 3 |
3 | Inspect for poor sensor ground circuit terminal 1 connection at the throttle position (TP) sensor. Is a repair necessary? | Go to Step 7 | Go to Step 4 |
4 | Inspect the TP signal circuit between TP sensor connector and the engine control module (ECM) for an intermittent short to voltage. Is a repair necessary? | Go to Step 8 | Go to Step 5 |
5 | Inspect for a poor sensor ground terminal M64 at the ECM. Is a repair necessary? | Go to Step 7 | Go to Step 6 |
6 | Inspect for an intermittent open or faulty splice in the sensor ground circuit. Is a repair necessary? | Go to Step 8 | Go to Diagnostic Aids |
7 | Repair or replace the faulty harness connector terminal for sensor ground circuit. Did you complete the repair? | Go to Step 9 | -- |
8 | Repair the intermittent open/short circuit in the wiring harness as needed. Did you complete the repair? | Go to Step 9 | -- |
9 |
Does the scan tool indicate that this diagnostic has run and passed? | Go to Step 10 | Go to Step 2 |
10 | Are any DTCs displayed that have not been diagnosed? | Go to applicable DTC table | System OK |
