Signal Sporadic. Permanent Fault

Safety
- See Safety instructions for handling fuel.
- Proceed to: Checking Diagnostic Trouble Codes section below.

Checking Diagnostic Trouble Codes
- Ignition OFF.
- Check fuel tank pressure sensor connector for contact resistance and oxidation and remedy.
- Check control module connector for contact resistance and oxidation and remedy.
- Check connector A1/A and A1/B for contact resistance and oxidation and remedy.
- Fuel tank pressure sensor connected.
- Control module connected.
- Start the engine and idle it.
- Wait 5 minutes.
- If EFI-621 is stored it should have intermittent status.

If reading is OK:
^ The cause of the diagnostic trouble code (DTC) has been loose connections in the fuel tank pressure sensor and/or the control module connectors.
^ Proceed to: Verification section below.

If reading is incorrect:
^ Proceed to: Checking Cables And Terminals section below.









Checking Cables And Terminals
- Check fuel tank pressure sensor and/or control module connector for loose connections.
- Check cable between fuel tank pressure sensor terminal 1 and control module # B15 for an intermittent open-circuit, an intermittent short-circuit to ground and an intermittent short-circuit to supply voltage.
- Check cable between fuel tank pressure sensor terminal 3 and control module # B31 for an intermittent open-circuit an intermittent short-circuit to ground and an intermittent short-circuit to supply voltage.
- Check cable between fuel tank pressure sensor terminal 2 and engine control module (ECM) # A18 for an intermittent open-circuit an intermittent short-circuit to ground and an intermittent short-circuit to supply voltage.
- The fuel tank pressure sensor power cable is connected inside the engine control module to the air conditioning (A/C) pressure sensor and accelerometer power cables.
- If anything happens to any of these cables all three will be affected.

Check Cables Between:
- Air conditioning pressure sensor terminal 3 and engine control module # B29.
- Accelerometer terminal 1 and engine control module # B1 for an intermittent short-circuit to supply voltage and an intermittent short-circuit to ground.
- Reinstall all components.
- Start the engine and idle it.
- Wait 5 minutes.
- Read off diagnostic trouble codes.
- If EFI-621 is stored it should have intermittent status.

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

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





Checking The Air Conditioning Pressure Sensor
- Ignition OFF.
- Fuel tank pressure sensor connected.
- Disconnect air conditioning pressure sensor.

NOTE: Diagnostic trouble codes may be stored for the air conditioning pressure sensor. Erase codes when fault-tracing is completed.

- Start the engine and idle it.
- Wait 5 minutes.
- Read off diagnostic trouble codes.
- If EFI-621 is stored it should have intermittent status.

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

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

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





Checking Accelerometer
- Ignition OFF.
- Fuel tank pressure sensor connected.
- Connect air conditioning pressure sensor.
- Disconnect accelerometer.

NOTE: Diagnostic trouble codes may be stored for the accelerometer. Erase codes when fault-tracing is completed.

- Start the engine and idle it.
- Wait 5 minutes.
- Read off diagnostic trouble codes.
- If EFI-621 is stored it should have intermittent status.

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

If reading is incorrect:
^ Proceed to: Replacing Component 2 sections below.

Replacing Component
- Try a new accelerometer.
- 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.
- Reconnect connectors and reinstall components.
- Disconnect the Volvo Scan Tool (ST) from the VIDA station and use it in stand-alone mode.
- Test drive the car.
- Use Volvo Scan Tool to read off diagnostic trouble codes.

- It EFI-621 is stored it should have intermittent status.

If reading is OK:
^ Fault corrected.

If reading is incorrect:
^ Fault not found.