Circuit Description
The engine control module (ECM) controls the throttle valves by applying a varying voltage to the throttle valve motor. The ECM monitors the actual throttle blade position using throttle position (TP) sensor 1 and sensor 2. The ECM tests the ability of the throttle blade to operate in the limp home throttle angle opening. When the correct operating conditions are met, the ECM will command the throttle blade to the limp home throttle angle opening. If the throttle blade does not operate in the desired throttle range, this diagnostic trouble code (DTC) will set.
Conditions for Running the DTC
| • | The vehicle speed is 0 km/h (0 mph). |
| • | The engine speed is less than 250 RPM. |
| • | The engine coolant temperature (ECT) is 5-100°C (41-212°F). |
| • | The intake air temperature (IAT) is more than 5°C (41°F). |
| • | The battery voltage is more than 10 volts. |
| • | The accelerator pedal position (APP) is less than 15 percent. |
Conditions for Setting the DTC
The TP angle is less than 2.1 percent or more than 9.8 percent, with the throttle at rest or at the limp-home position.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
The throttle valves are spring loaded to a slightly open position. The throttle valves should be open approximately 3-5 percent. This is referred to as the rest position. The throttle valves should not be completely closed nor should they be open any more than the specified amount. The throttle valves should move open and to the closed position without binding under the normal spring pressure. The throttle should NOT be free to move open or closed WITHOUT spring pressure. Replace the throttle body if any of these conditions are found.
The scan tool has the ability to operate the throttle control system using Special Functions. Actuate the throttle valves using the throttle position function located in the throttle actuator control (TAC) system menu. This function will operate the throttle valve through the entire range in order to determine if the throttle body and system operate correctly.
Check for the following conditions:
| • | Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector. |
| • | Poor connections at the ECM or at the component--Inspect the harness connectors for a poor terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems for the proper procedure. |
| • | Refer to Symptoms - Engine Controls for the intermittents. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
The throttle valves are spring loaded in a slightly open position and should move in either direction without binding. The throttle valves should always be under spring pressure.
-
When the ignition is turned ON, the ECM operates the throttle control motor to verify the integrity of the system prior to start-up. This can be seen by the momentary flash of the test lamp as the ignition is turned ON.
Step | Action | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | |||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |||||||
2 | With a scan tool, observe the DTC information. Are any accelerator pedal position (APP) or TP sensor DTCs set? | Go to Step 3 | |||||||
Did you find any of these conditions with the throttle body? | Go to Step 14 | Go to Step 4 | |||||||
4 |
Important: The test lamp may momentarily flash when testing these circuits. This is considered normal.
Did the test lamp illuminate and remain illuminated on either circuit? | Go to Step 7 | Go to Step 5 | ||||||
5 |
Important: The test lamp may momentarily flash when testing these circuits. This is considered normal. Probe the throttle valve motor + and - circuit terminals with the test lamp connected to battery positive. Did the test lamp illuminate and remain illuminated on either circuit? | Go to Step 8 | Go to Step 6 | ||||||
Does the test lamp flash ON and then turn OFF? | Go to Step 12 | Go to Step 9 | |||||||
7 |
Does the test lamp illuminate? | Go to Step 10 | Go to Step 13 | ||||||
8 |
Does the test lamp illuminate? | Go to Step 11 | Go to Step 13 | ||||||
9 |
Did you find and correct the condition? | Go to Step 16 | Go to Step 13 | ||||||
10 | Repair the short to voltage on the circuit where the test lamp remained illuminated. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 16 | -- | ||||||
11 | Repair the short to ground on the circuit where the test lamp remained illuminated. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 16 | -- | ||||||
12 | Test for a poor connection or terminal tension at the throttle body connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 16 | Go to Step 14 | ||||||
13 | Test for a poor connection or terminal tension at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 16 | Go to Step 15 | ||||||
14 | Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement . Did you complete the replacement? | Go to Step 16 | -- | ||||||
15 |
Important:
Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the action? | Go to Step 16 | -- | ||||||
16 |
Does the DTC run and pass? | Go to Step 17 | Go to Step 2 | ||||||
17 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | System OK | |||||||
