Signal Too Low. Permanent Fault

Safety
- See Safety instructions for handling fuel.
- Proceed to: Checking Power Cable section below.





Checking Power Cable
- Ignition OFF.
- Wait for approximately 150 seconds (cars with immobilizer 245 seconds).
- Disconnect tank pressure sensor.
- Connect an ohmmeter between fuel tank pressure sensor connector terminal 1 (engine control module (ECM) side) and ground.
- The ohmmeter should read approximately 0.2 - 1.5 k ohms.

If reading is OK:
^ Proceed to: Checking Cable section below.

If value is lower:
^ Proceed to: Checking Accelerometer section below.

If value is higher:
^ Proceed to: Checking Connector section below.





Checking Accelerometer
- Ignition OFF.
- Tank pressure sensor disconnected.
- Disconnect accelerometer.
- Connect an ohmmeter between fuel tank pressure sensor connector terminal 1 (engine control module side) and ground.
- The ohmmeter should read 0.2 - 1.5 k ohms.

If reading is OK:
^ Proceed to: Replacing Component section below.

If reading is incorrect:
^ Proceed to: Checking The Air Conditioning Pressure Sensor section below.





Replacing Component
- Try a new accelerometer.
- Proceed to: Verification section below.





Checking The Air Conditioning Pressure Sensor
- Ignition OFF.
- Fuel tank pressure sensor and accelerometer disconnected.
- Disconnect the air conditioning (A/C) pressure sensor.
- Connect an ohmmeter between fuel tank pressure sensor connector terminal 1 (engine control module side) and ground.
- The ohmmeter should read 0.2 - 1.5 k ohms.

If reading is OK:
^ Proceed to: Replacing Component section below.

If reading is incorrect:
^ Proceed to: Checking Short-circuit section below.





Replacing Component
- Try a new air conditioning pressure sensor.
- Proceed to: Verification section below.





Checking Short-circuit
- The fuel tank pressure sensor power cable is connected inside the engine control module to the accelerometer and air conditioning pressure sensor power cables.
- If anything happens to any of these cables all three will be affected.

Check Cables Between:
- Tank pressure sensor terminal 1 and engine control module # B15.
- Accelerometer terminal 1 and engine control module # B1.
- Air conditioning pressure sensor terminal 3 and engine control module # B29 for a short-circuit to ground.
- Remedy as necessary.
- Proceed to: Verification section below.





Checking Connector
- Ignition OFF.
- Tank pressure sensor disconnected.
- Check control module connector and connector A1/A for contact resistance and oxidation and remedy.
- Control module connected.
- Reconnect connector A1/A.
- Connect an ohmmeter between fuel tank pressure sensor connector terminal 1 (engine control module side) and ground.
- The ohmmeter should read 0.2 - 1.5 k ohms

If reading is OK:
^ Proceed to: Verification section below.

If reading is incorrect:
^ Proceed to: Checking Cable section below.





Checking Cable
- Check power cable between fuel tank pressure sensor terminal 1 and engine control module # B15 for an open-circuit.
- Remedy as necessary.
- Proceed to: Verification section below.





Checking The Signal Cable
- Ignition OFF.
- Tank pressure sensor disconnected.
- Ignition ON.
- Connect a voltmeter between the fuel tank pressure sensor connector terminal 3 (engine control module side) and ground.
- The voltmeter should read approximately 5 - 6 Volts.

If reading is OK:
^ Proceed to: Replacing Component section below.

If reading is incorrect:
^ Proceed to: Checking Cable section below.





Checking Cable
- Check signal cable between fuel tank pressure sensor terminal 3 and engine control module # B31 for an open-circuit.
- Remedy as necessary.
- Proceed to: Verification section below.





Replacing Component
- Try a new fuel tank pressure sensor.
- Proceed to: Verification section below.

Verification
After carrying out the repair, check that the fault has been remedied as follows:

- Ignition OFF.
- Ensure that fuel tank pressure sensor, air conditioning pressure sensor, accelerometer and engine control module are connected.
- Connector A1/A and A1/B connected.
- Start the engine and idle it.

- If EFI-621 is stored it should have intermittent status.
- Does EFI-621 have intermittent status?

Yes:
^ Fault corrected.

No:
^ Fault not found.