Signal Too Low. Permanent Fault

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 3 (engine control module (ECM) side) and ground.

The ohmmeter should read approximately 0.2 - 1.5K ohms.

If reading is OK:
^ Proceed to Checking the signal cable section below.

If value is lower:
^ Proceed to next step 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 3 (engine control module (ECM) side) and ground.

The ohmmeter should read 0.2 - 1.5K ohms.

If reading is OK:
^ Proceed to next step below.

If reading is incorrect:
^ Proceed to Checking the air conditioning (A/C) pressure sensor section below.






Replacing component
Try a new accelerometer.

Then continue with:
^ Verification section below.











Checking the air conditioning (A/C) 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 3 (engine control module (ECM) side) and ground.

The ohmmeter should read 0.2 - 1.5K ohms.

If reading is OK:
^ Proceed to next step below.

If reading is incorrect:
^ Proceed to Checking atmospheric pressure sensor section below.






Replacing component
Try a new air conditioning (A/C) pressure sensor.

Then continue with:
^ Verification section below.












Checking atmospheric pressure sensor
- Ignition off.
- Fuel tank pressure sensor, accelerometer and air conditioning (A/C) pressure sensor disconnected.
- Disconnect atmospheric pressure sensor.
- Connect an ohmmeter between fuel tank pressure sensor connector terminal 3 (engine control module (ECM) side) and ground.

The ohmmeter should read 0.2 - 1.5K ohms.

If reading is OK:
^ Proceed to next step below.

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





Replacing component
Try a new atmospheric pressure sensor.

Then continue with:
^ Verification section below.














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

Check cables between:
- Tank pressure sensor terminal 3 and engine control module (ECM) #B15.
- Accelerometer terminal 1 and engine control module (ECM) #B1.
- Air conditioning (A/C) pressure sensor terminal 3 and engine control module (ECM) #B29 for a short-circuit to ground. Remedy as necessary.

Then continue with:
^ Verification section below.


















Checking connector
- Ignition off.
- Tank pressure sensor disconnected.
- Check control module connector and connectors 24/2 and 24/4 for contact resistance and oxidation and remedy.
- Control module connected.
- Reconnect connectors 24/2 and 24/4.
Connect an ohmmeter between fuel tank pressure sensor connector terminal 3 (engine control module (ECM) side) and ground.

The ohmmeter should read 0.2 - 1.5K ohms.

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

If reading is incorrect:
^ Proceed to next step below.











Checking cable
Check voltage between fuel tank pressure sensor terminal 3 and control module #B15 for an open-circuit.

Then continue with:
^ Verification section below.















Checking the signal cable
- Tank pressure sensor disconnected.
- Ignition on.
Connect a voltmeter between the fuel tank pressure sensor connector terminal 2 (engine control module (ECM) 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 next step below.












Checking cable
Check signal cable between fuel tank pressure sensor terminal 2 and control module B31 for an open-circuit.

Then continue with:
^ Verification section below.


Replacing component
Try a new fuel tank pressure sensor. See: Fuel Tank Pressure Sensor.

Then continue with:
^ Verification section below.








Verification


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


- Ignition off
- Ensure that fuel tank pressure sensor, air conditioning (A/C) pressure sensor, accelerometer and engine control module (ECM) are connected.
- Connectors 24/2 and 24/4 are 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