Circuit Description
The DTC P2555 Throttle Actuator Control (TAC) Inhibit Circuit High Voltage diagnostic detects a fault in the TAC motor control circuit. The powertrain control module (PCM) receives accelerator pedal position (APP) sensor information and calculates the desired throttle position. The PCM sends this desired throttle position or target value to the TAC module. The TAC module achieves the desired throttle position by commanding the throttle control motor to position the throttle valve at the target value. The TAC module then compares the throttle position (TP) sensor 1 value to the target value. If necessary, the throttle control motor is moved slightly in order to obtain the exact target value position. If the TAC motor control circuit voltage is too high, DTC P2555 sets. The TAC motor and circuitry are integral parts of the TAC module and are not serviced separately. The TAC module is not serviceable and must be replaced with the throttle body assembly. For additional information on the operation of the TAC system, refer to Throttle Actuator Control (TAC) System Description .
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P2555 Throttle Actuator Control (TAC) Inhibit Circuit High Voltage
Conditions for Running the DTC
| • | Before the PCM can report DTC P2555 failed, DTC P2554 must run and pass. |
| • | The ignition is ON. |
| • | DTC P2555 runs continuously once the above conditions are met. |
Conditions for Setting the DTC
| • | The PCM has detected a lower than expected voltage on the TAC motor control circuit, when the motor is inactive, or a higher than expected voltage when the motor is active. |
| • | The above conditions is present for at least 160 milliseconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL). |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after 3 consecutively passing trips without a fault present. |
| • | A history DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Perform the scan tool Clear DTC Information function. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
The Diagnostic System Check - Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool, if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
-
The normal voltage reading is approximately 0.67 volt. If the conditions for a DTC P2555 are present, the circuit voltage would default to 0 volts.
-
This step checks for an open in the TAC module electrical grounds. The TAC module can not operate correctly if there are faulty electrical grounds.
-
After replacing the TAC module, a new minimum throttle position and idle speed must also be established.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||
Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | ||
2 |
Is a DTC P2555 set? | -- | Go to Step 4 | Go to Step 3 |
Is the voltage within the specified range? | 0.63-0.70 V | Go to Intermittent Conditions | Go to Step 4 | |
4 |
Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 5 |
Probe each throttle actuator control (TAC) module ground circuit with a test lamp connected to B+. Did the test lamp illuminate on both ground circuits? | -- | Go to Step 7 | Go to Step 6 | |
6 | Repair the open in the ground circuits of the TAC module. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 9 | -- |
7 |
Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 8 |
Did you complete the replacement? | -- | Go to Step 9 | -- | |
9 |
Does the DTC run and pass? | -- | Go to Step 10 | Go to Step 2 |
10 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
