Signal Too Low. Permanent Fault

SIGNAL TOO LOW. PERMANENT FAULT





Checking Power Cable

- Ignition OFF.
- Disconnect atmospheric pressure sensor.
- Ignition ON.
- Connect a voltmeter between atmospheric pressure sensor connector terminal 1 and ground.

The voltmeter should read 5 Volts.

It reading is OK:
- Proceed to test step below.

If reading is incorrect:
- Proceed to Checking Power Cable Resistance to Ground section below.





Checking Signal Cable Resistance

- Ignition OFF.
- Wait for approx. 150 seconds (cars with immobilizer 245 seconds).
- Atmospheric pressure sensor disconnected.
- Connect an ohmmeter between atmospheric pressure sensor connector 3 and ground.

The ohmmeter reading should be higher than 0.2 Meg Ohms.

If reading is OK:
- Proceed to test step below.

If reading is incorrect:
- Check the cable between atmospheric pressure sensor terminal 3 and engine control module (ECM) #B22 for a short-circuit to ground.
- Then proceed to Verification section below.





Checking Atmospheric Pressure Sensor

- Ignition OFF.
- Connect atmospheric pressure sensor.
- START the engine and idle it.
- Go into scrolling value list.
- Read off atmospheric pressure sensor signal.

This value should be approx. 4.5 Volts at sea level and normal atmospheric pressure.

If reading is OK
- The cause of the diagnostic trouble code (DTC) has been loose connections in the atmospheric pressure sensor connector.
- Check connector for contact resistance and oxidation and remedy.
- Then proceed to Verification section below.

If reading is incorrect:
- Try a new atmospheric pressure sensor.
- Then proceed to Verification section below.





Checking power Cable Resistance to Ground

- Ignition OFF.
- Atmospheric pressure sensor disconnected.
- Wait for approx. 150 seconds (cars with immobilizer 245 seconds).
- Connect an ohmmeter between atmospheric pressure sensor connector 1 and ground.

The ohmmeter should read approx. 0.2 - 1.5K Ohms.

If value is Lower:
- Proceed to test step below.

If value is Higher:
- Proceed to Checking Engine Control Module Connector section below.





Checking Accelerometer

- Ignition OFF.
- Atmospheric pressure sensor disconnected.
- Disconnect accelerometer.
- Connect an ohmmeter between atmospheric pressure sensor connector 1 and ground.

The ohmmeter should read approx. 0.2 - 1.5K Ohms.

If reading is OK:
- Try a new accelerometer.
- Then proceed to Verification section below.

If reading is incorrect:
- Proceed to test step below.





Checking Fuel Tank Pressure Sensor

- Ignition OFF.
- Atmospheric pressure sensor disconnected.
- Accelerometer disconnected.
- Disconnect fuel tank pressure sensor.
- Connect an ohmmeter between atmospheric pressure sensor connector 1 and ground.

The ohmmeter should read approx. 0.2 - 1.5K Ohms.

If reading is OK:
- Try a new tank pressure sensor.
- Then proceed to Verification section below.

If reading is incorrect:
- Proceed to test step below.





Checking the Air Conditioning Pressure Sensor

- Ignition OFF.
- Atmospheric pressure sensor, fuel tank pressure sensor and accelerometer disconnected.
- Disconnect the A/C pressure sensor.
- Ignition ON.
- Connect ohmmeter between atmospheric pressure sensor terminal 1 and ground.

The ohmmeter should read approx. 0.2 - 1.5K Ohms.

If reading is OK:
- Try a new air conditioning (A/C) pressure sensor.
- Then proceed to Verification section below.

If reading is incorrect:
- Proceed to test step below.





Checking for a Short-Circuit

The atmospheric pressure sensor power cable is connected inside the engine control module (ECM) to the air conditioning (A/C) pressure sensor, fuel tank prnssure sensor and accelerometer power cables. If anything happens to any of these cables all four will be affected.

Check cables between:

- Air conditioning (A/C) pressure sensor terminal 3 and engine control module (ECM) #B29.
- Tank pressure sensor terminal 1 and engine control module (ECM) #B15.
- Accelerometer terminal 1 and engine control module (ECM) #B1.
- Atmospheric pressure sensor terminal 1 and engine control module (ECM) #B29.

For a short-circuit to supply voltage.

- Then proceed to Verification section below.





Checking Engine Control Module Connector

- Ignition OFF.
- Atmospheric pressure sensor disconnected.
- Check engine control module (ECM) connector for contact resistance and oxidation and remedy.
- Engine control module (ECM) connected.
- Connect an ohmmeter between atmospheric pressure sensor connector 1 and ground.

The ohmmeter should read approx. 0.2 - 1.5K Ohms.

If reading is OK:
- The diagnostic trouble code (DTC) has been caused by loose connections in the engine control module (ECM) connector.
- Then proceed to Verification section below.

If reading is incorrect:
- Check cable between atmospheric pressure sensor terminal 31 and engine control module (ECM) #B29 for an open-circuit.
- Then proceed to Verification section below.

Verification

Hint: Affer carrying out the repair, check that the fault has been remedied as follows.

- Ignition OFF.
- Reconnect connectors and reinstall components.
- START the engine and idle it.
- Wait for a minute.
- Read off diagnostic trouble codes (DTCs).

If EFI-422 is stored it should have intermittent fault status.

Alternative Intermittent:
- Fault corrected.

Alternative Permanent:
- Proceed to test step below.

Fault-tracing Information

- The verification result shows that the fault persists.
- Do you want to exit fault-tracing?

Yes:
- Fault not corrected.

No:
- Return to Checking Power Cable section above.