P2174 Low Airflow/Restriction Detected (Instantaneous Accumulation)
September 28, 2018
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P2174 code - This diagnostic runs continuously when the following are met with the engine running at or above idle (not cranking), no MAP sensor DTCs, no throttle body related DTCs, no 5-volt reference DTCs, no crank/cam sensor DTCs. The PCM calculated MAP value is greater than actual MAP value plus an offset value. The ETC light will flash and the MIL light will illuminate.
- Resistance in the 5-volt supply circuit
- Resistance in the MAP signal circuit
- Resistance in MAP sensor ground circuit
- MAP sensor
- Powertrain Control Module (PCM)
Diagnose any 5-volt supply, TPS, Cam sensor, Crank sensor or MAP sensor DTC before continuing.
The most likely cause of this DTC is a plugged intake air system or dirty Throttle Body. Check for any service bulletins before continuing. Check for any aftermarket components or modifications to the air intake system. Question the customer about weather conditions, as ice build up on the throttle blade can cause this fault when the ambient air temperature in the -10°C (14°F) to 4°C (39°F) range.
Start the engine and allow it to idle until closed loop fueling is archived. With a scan tool, read DTC.
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 engine 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.
Compare the scan tool reading to the vacuum gauge reading?
Both of the readings match, remove the air cleaner assembly and check for restriction in the filter or assembly. Check for restriction in the air inlet plumbing. Check the throttle body for any signs of binding, sticking or obstructions.
Engine vacuum is normal and MAP reading on the 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 3.0 Ohms?
Yes, go to step 4.
No, repair the 5-volt supply circuit for high resistance.
Step 4. Check for high resistance in the MAP sensor circuit
Measure the resistance of the MAP signal circuit between the MAP sensor harness connector and PCM harness connector.
Is the resistance below 3.0 Ohms?
Yes, go to step 5.
No, repair the MAP signal circuit for high resistance.
Step 5. Check for high resistance in the sensor ground circuit
Measure the resistance of the sensor ground circuit between the MAP sensor harness connector and PCM harness connector.
Is the resistance below 3.0 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 archieved. With the scan tool read DTCs.
Did the DTC return?
Yes, go to step 8.
No, repair is complete.
Step 8. Powertrain Control Module (PCM)
Using the wiring diagram/schematic as a giuide, inspect the wiring and connectors between the MAP sensor, throttle body, and the Powertrain Control Module (PCM). Look for any chafed, pierced, pinched, or partially broken wires. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the MAP sensor. thorttle body, and Powertrain Control Module (PCM) connectors. Perform the service bulletins that may apply.
Were there any problems found?
Yes, repair as neccesary.
No, replace and program the Powertrain Control Module (PCM). Perform the Powertrain verification test.
Possible causes P2174 code
- Restriction in the air inlet system- Resistance in the 5-volt supply circuit
- Resistance in the MAP signal circuit
- Resistance in MAP sensor ground circuit
- MAP sensor
- Powertrain Control Module (PCM)
Diagnostic test P2174 code
Step 1. Check For an active DTCDiagnose any 5-volt supply, TPS, Cam sensor, Crank sensor or MAP sensor DTC before continuing.
The most likely cause of this DTC is a plugged intake air system or dirty Throttle Body. Check for any service bulletins before continuing. Check for any aftermarket components or modifications to the air intake system. Question the customer about weather conditions, as ice build up on the throttle blade can cause this fault when the ambient air temperature in the -10°C (14°F) to 4°C (39°F) range.
Start the engine and allow it to idle until closed loop fueling is archived. With a scan tool, read DTC.
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 engine 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.
Compare the scan tool reading to the vacuum gauge reading?
Both of the readings match, remove the air cleaner assembly and check for restriction in the filter or assembly. Check for restriction in the air inlet plumbing. Check the throttle body for any signs of binding, sticking or obstructions.
Engine vacuum is normal and MAP reading on the 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 3.0 Ohms?
Yes, go to step 4.
No, repair the 5-volt supply circuit for high resistance.
Step 4. Check for high resistance in the MAP sensor circuit
Measure the resistance of the MAP signal circuit between the MAP sensor harness connector and PCM harness connector.
Is the resistance below 3.0 Ohms?
Yes, go to step 5.
No, repair the MAP signal circuit for high resistance.
Step 5. Check for high resistance in the sensor ground circuit
Measure the resistance of the sensor ground circuit between the MAP sensor harness connector and PCM harness connector.
Is the resistance below 3.0 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 archieved. With the scan tool read DTCs.
Did the DTC return?
Yes, go to step 8.
No, repair is complete.
Step 8. Powertrain Control Module (PCM)
Using the wiring diagram/schematic as a giuide, inspect the wiring and connectors between the MAP sensor, throttle body, and the Powertrain Control Module (PCM). Look for any chafed, pierced, pinched, or partially broken wires. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the MAP sensor. thorttle body, and Powertrain Control Module (PCM) connectors. Perform the service bulletins that may apply.
Were there any problems found?
Yes, repair as neccesary.
No, replace and program the Powertrain Control Module (PCM). Perform the Powertrain verification test.
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