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P2172






P2172-HIGH AIRFLOW/VACUUM LEAK DETECTED (INSTANTANEOUS ACCUMULATION)

Special Tools:






For a complete wiring diagram, refer to the Wiring Information.

Theory of operation

The Electronic Throttle Control (ETC) motor is controlled by the Powertrain Control Module (PCM). The DC motor located in the throttle body drives the throttle blade. In order to decrease idle speed, along with spark and fuel delivery changes the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate.

- When Monitored:
Ignition on and engine running with no MAP Sensor DTCs.

- Set Condition:
A large vacuum leak has been detected or both of the TP Sensors have failed based on their position being 2.5 Volts and the calculated MAP value is less than the actual MAP minus an Offset value. One trip fault and the code will set within five seconds. ETC light will flash.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. ACTIVE DIAGNOSTIC TROUBLE CODE (DTC)

NOTE: The most likely cause of this DTC is a vacuum leak.

NOTE: This fault code could be present if any Camshaft or Crankshaft Position Sensor DTCs are set. No repair is necessary for P2172 if any Camshaft or Crankshaft Position Sensor DTCs are set.

NOTE: Diagnose any 5 Volt Supply, TP Sensor, Fuel System Lean or Rich or MAP Sensor DTCs before continuing.

NOTE: The throttle plate should be free from binding and carbon build up.

1. Ignition on, engine not running.
2. With the scan tool, read the active DTCs.

Is the DTC Active at this time?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.

2. VACUUM LEAK

NOTE: This code is enabled on engines with a plastic intake manifold and is intended to limit the maximum engine speed if a large crack occurs.

NOTE: A large vacuum leak is most likely the cause of this DTC.

1. Inspect the Intake Manifold and Throttle Body for leaks and cracks.
2. Inspect the Power Brake Booster for any vacuum leaks.
3. Inspect the PCV system for proper operation and any vacuum leaks.
4. Inspect the MAP Sensor for proper installation.

Were any vacuum leaks found?

Yes

- Repair the vacuum leak as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 3

3. MAP SENSOR OPERATION
1. Start the engine.
2. With the scan tool, monitor the MAP Sensor voltage.
3. Snap the Accelerator pedal.

Does the MAP Sensor voltage vary from below 2.0 Volts at idle to above 3.5 Volts at Wide Open Throttle?

Yes

- Go To 4

No

- Go To 13

4. TP SENSOR OPERATION
1. Ignition on, engine not running.
2. With the scan tool, perform the ETC Throttle Follower Test.
3. TP Sensor No.1 should start at approximately 0.7 of a Volt and increase to 4.3 Volts.
4. TP Sensor No.2 should start at approximately 4.3 Volts and decrease to 0.7 of a Volt.

Is the voltage transition smooth between the appropriate values?

Yes

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.

No

- Go To 5

5. RESISTANCE IN THE (F855) 5 VOLT SUPPLY CIRCUIT
1. Turn the ignition off.
2. Disconnect the Throttle Body harness connector.
3. Disconnect the C2 PCM harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the PCM Pinout Box (8815A) to perform diagnosis.

4. Measure the resistance of the (F855) 5 Volt Supply circuit from the Throttle Body harness connector to the appropriate terminal of PCM Pinout Box.

Is the resistance above 100 Ohms?

Yes

- Go To 6

No

- Repair the excessive resistance in the (F855) 5 Volt Supply circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

6. (F855) 5 VOLT SUPPLY CIRCUIT SHORTED TO GROUND
1. Measure the resistance between ground and (F855) 5 Volt Supply circuit at the Throttle Body harness connector.

Is the resistance above 100 Ohms?

Yes

- Go To 7

No

- Repair the short to ground in the (F855) 5 Volt Supply circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

7. TP SENSOR
1. Connect the C2 PCM harness connector.
2. Ignition on, engine not running.
3. With the scan tool, monitor the TP Sensor voltage.
4. Connect a jumper wire between the (K22) TP Sensor No.1 Signal circuit and the (K922) TP Sensor Return circuit in the Throttle Body harness connector.
5. TP Sensor No.1 voltage should start at approximately 4.8 Volts and decrease to 0.2 of a Volt.
6. Connect a jumper wire between the (K122) TP Sensor No.2 Signal circuit and the (F855) 5 Volt Supply circuit in the Throttle Body harness connector.
7. TP Sensor No.2 voltage should start at approximately 0 Volts and increase to 4.8 to 5.2 Volts.

Does the TP Sensor voltage change to the appropriate voltage with the jumper wire installed?

Yes

- Verify that there is good pin to terminal contact in the Throttle Body and Powertrain Control Module connectors. Disconnect the Battery before replacing the Throttle Body Assembly. If OK, replace the Throttle Body Assembly. After installation is complete, use a scan tool and select the ETC RELEARN function
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 8

8. RESISTANCE IN THE (K22) TP SENSOR NO.1 SIGNAL CIRCUIT
1. Turn the ignition off.
2. Disconnect the C2 PCM harness connector.
3. Measure the resistance of the (K22) TP Sensor No.1 Signal circuit from the Throttle Body harness connector to the appropriate terminals of PCM Pinout Box.

Is the resistance below 5.0 Ohms?

Yes

- Go To 9

No

- Repair the excessive resistance in the (K22) TP Sensor No.1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

9. RESISTANCE IN THE (K122) TP SENSOR NO.2 SIGNAL CIRCUIT
1. Measure the resistance of the (K122) TP Sensor No.2 Signal circuit from the Throttle Body harness connector to the appropriate terminals of PCM Pinout Box.

Is the resistance below 5.0 Ohms?

Yes

- Go To 10

No

- Repair the excessive resistance in the (K122) TP Sensor No.2 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

10. (K22) TP SENSOR NO.1 SIGNAL CIRCUIT SHORTED TO GROUND
1. Measure the resistance between ground and the (K22) TP Sensor No.1 Signal circuit at the Throttle Body harness connector.

Is the resistance above 100 Ohms?

Yes

- Go To 11

No

- Repair the short to ground in the (K22) TP Sensor No.1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

11. (K122) TP SENSOR NO.2 SIGNAL CIRCUIT SHORTED TO GROUND
1. Measure the resistance between ground and the (K122) TP Sensor No.2 Signal circuit at the Throttle Body harness connector.

Is the resistance above 100 Ohms?

Yes

- Go To 12

No

- Repair the short to ground in the (K122) TP Sensor No.2 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

12. RESISTANCE IN THE (K922) TP SENSOR RETURN CIRCUIT
1. Measure the resistance of the (K922) TP Sensor Return circuit from the Throttle Body harness connector to the appropriate terminal of PCM Pinout Box.

Is the resistance below 5.0 Ohms?

Yes

- Go To 19

No

- Repair the excessive resistance in the (K922) TP Sensor Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

13. RESISTANCE IN THE (F856) 5 VOLT SUPPLY CIRCUIT




1. Turn the ignition off.
2. Disconnect the MAP Sensor harness connector.
3. Disconnect the C1 PCM harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the PCM Pinout Box (8815A) to perform diagnosis.

4. Measure the resistance of the (F856) 5 Volt Supply circuit from the MAP Sensor harness connector to the appropriate terminal of PCM Pinout Box.

Is the resistance below 5.0 Ohms?

Yes

- Go To 14

No

- Repair the excessive resistance in the (F856) 5 Volt Supply circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

14. (F856) 5 VOLT SUPPLY CIRCUIT SHORTED TO GROUND




1. Measure the resistance between ground and the (F856) 5 Volt Supply circuit in the MAP Sensor harness connector.

Is the resistance above 100k Ohms?

Yes

- Go To 15

No

- Repair the short to ground in the (F856) 5 Volt Supply circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

15. MAP SENSOR




1. Connect the C1 PCM harness connector.
2. Ignition on, engine not running.
3. With the scan tool, monitor the MAP Sensor voltage.
4. Connect a jumper wire between the (K1) MAP Signal circuit and the (K900) Sensor ground circuit in the MAP Sensor harness connector.
5. Cycle the ignition switch from off to on.
6. With the scan tool, monitor the MAP Sensor voltage.

Does the scan tool display MAP voltage from approximately 4.9 Volts to below 0.5 Volt with the jumper wire installed?

Yes

- Verify that there is good pin to terminal contact in the MAP Sensor and Powertrain Control Module connectors. If OK, replace the MAP Sensor. Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 16
NOTE: Remove the jumper wire before continuing.


16. RESISTANCE IN THE (K1) MAP SIGNAL CIRCUIT




1. Turn the ignition off.
2. Disconnect the C2 PCM harness connector.
3. Measure the resistance of the (K1) MAP Signal circuit from the MAP Sensor harness connector to the appropriate terminal of PCM Pinout Box.

Is the resistance below 5.0 Ohms?

Yes

- Go To 17

No

- Repair the excessive resistance in the (K1) MAP Signal circuit
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

17. (K1) MAP SIGNAL CIRCUIT SHORTED TO GROUND




1. Measure the resistance between ground and the (K1) MAP Signal circuit in the MAP Sensor harness connector.

Is the resistance above 100k Ohms?

Yes

- Go To 18

No

- Repair the short to ground in the (K1) MAP Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

18. RESISTANCE IN THE (K900) SENSOR GROUND CIRCUIT




1. Measure the resistance of the (K900) Sensor ground circuit from the MAP Sensor harness connector to the appropriate terminal of PCM Pinout Box.

Is the resistance below 5.0 Ohms?

Yes

- Go To 19

No

- Repair the excessive resistance in the (K900) Sensor ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

19. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the MAP Sensor, Throttle Body and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the MAP Sensor, Throttle Body and Powertrain Control Module connectors.
4. Perform any Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Powertrain Control Module. Powertrain Control Module - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

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