P2173 High Airflow/Vacuum Leak Detected (Slow Accumulation)

P2173 code - The Powertrain Control Module (PCM) uses the Manifold Absolute Pressure (MAP) sensor base model and the Electronic Throttle Control (ETC) motor position value to create a calculated MAP model value. This calculated MAP model is then compared to the actual MAP sensor signal input to the PCM. The PCM uses this comparison to detect vacuum leaks or restriction in the intake air system. The purpose of this monitor is to detect an instantaneous or gradual change in the intake manifold vacuum that exceeds the calibrated high or low thresholds.

The PCM detects a gradual long term increase in the difference between the actual Map Pressure sense and calculated map sensor value, beyond the calibrated adaptive limit, due to a loss of vacuum. When monitored this DTC the engine running at or above idle (not cranking). No MAP sensor, throttle body, CMP/CKP sensor or 5.0 Volt reference DTCs. Default actions the ETC ligh flash and the MIL ligh illuminate.

Possible causes P2173 code

- Cavuum leak
- Restriction in the exhaust system
- Internal engine mechanical components
- Resistance in the 5-volt supply circuit
- Resistance in the in the MAP signal circuit
- Resistance in MAP sensor ground circuit
- MAP sensor
- Powertrain Control Module (PCM)

Diagnostic test P2173 code

Step 1. Check for an active DTC
Diagnose any 5-volt supply, TPS, Cam sensor, Crank sensor or MAP sensor DTCs before continuing.
Start the engine and allow it to idle until closed loop fueling is archived.
With the scan tool, read DTCs.

Is the DTC active or pending?

Yes, go to step 2.
No, perform the PCM intermittent condition.

Step 2. Compare the engine vacuum and MAP sensor reading
Turn the ignition off.
Connect a vacuum gauge to the intake manifold.
Start the engine and allow it to idle.
Monitor the reading on the vacuum gauge.
Monitor the MAP sensor reading on the scan tool.

The minimum engine vacuum at idle should be no less than approximately 13.0 HG.

Compare the scan tool reading to the vacuum gauge reading?

Both of the readings match and are below 13.0 HG, check and repair any engine leaks, exhaust restrictions, or engine mechanical conditions that can cause low engine compression.

Engine vacuum is normal and MAP reading on scan tool does not match, go to step 3.

Step 3. Check for high resistance in the 5-volt supply circuit
Turn the ignition off.
Disconnect the MAP sensor harness connector.
Disconnect the PCM harness connector.
Measure the resistance of the 5-volt supply circuit between the MAP sensor harness connector and PCM harness connector.

Is the resistance below 5.0 Ohms?

Yes, go to step 4.
No, reapir the 5-volt supply circuit for high resistance.

Step 4. Check for high resistance in the MAP signal circuit
Measure the resistance of the MAP signal circuit between the MAP sensor harness connector and the PCM harness connector.

Is the resistance below 5.0 Ohms?

Yes, go to step 5.
No, repair the MAP signal circuit for high resistance.

Step 5. Chech for high resistance in the sensor ground circuit
Measure the resistance of the sensor ground circuit between the MAP sensor connector and PCM harness connector.

Is the resistance below 5.0 Ohms?

Yes, go to step 6.
No, repair the excessive sensor ground circuit for high resistance.

Step 6. Check the MAP sensor and port for obstructions
Remove the MAP sensor.
Inspect the MAP sensor and port for any obstructions.

Were any obstructions found?

Yes, perform the appropriate repairs and retest.
No, go to step 7.

Step 7. MAP sensor
Replace the MAP sensor.
Turn the ignition on.
With the scan tool erase DTCs.
Start the engine and allow it to idle until closed loop fueling is archived.
With the scan tool read DTCs.

Did the DTC return?

Yes, go to step 8.
No, repair complete.

Step 8. Check related PCM and component connections

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