Pinpoint Test 2: Incorrect Fuel Gauge Indication

PINPOINT TEST 2: INCORRECT FUEL GAUGE INDICATION

Normal Operation

The fuel level sender (part of the fuel pump module) is hardwired to the instrument cluster between the signal circuit (Y/V) and the signal return circuit (G/L), which is grounded internally within the instrument cluster. The fuel level sender is a variable resistor that ranges from 10 ohms ± 2 ohms at full (F) and 180 ohms ± 4 ohms at empty (E). The instrument cluster provides a reference voltage to the fuel pump module on circuit (Y/V). As the fuel level changes, a float actuates a variable resistor on the fuel pump sender and raises or lowers the fuel level signal voltage depending on the resistance of the fuel level sender. The instrument cluster monitors the changes in voltage and commands the fuel gauge with a corresponding movement of the pointer.The instrument cluster uses 4 different operating modes to calculate the fuel level:

- Anti-slosh (default mode)
- Key OFF fueling

- Key ON fueling

- Recovery After a fuel fill up, the time for the fuel gauge to move from empty (E) to full (F) ranges from 2 seconds to 55 minutes depending on which operating mode the fuel gauge is in.
The default fuel gauge mode is called the anti-slosh mode. To prevent fuel gauge changes from fuel slosh (gauge instability due to changes in fuel sender readings caused by fuel moving around in the tank), the fuel gauge takes approximately 55 minutes to go from empty (E) to full (F).The key OFF fueling mode (2 seconds to read empty [E] to full [F]) requires 3 conditions be met:

- The key must be in the OFF position when refueling the vehicle.
- At least 15% of the vehicle's fuel capacity must be added to the fuel tank.
- The instrument cluster must receive a valid key ON fuel sender reading within 1 second of the key being put into the RUN position. The key ON sample readings are considered valid if the fuel sender reading is between 10 ohms ± 2 ohms and 180 ohms ± 4 ohms.If these conditions are not met, the fuel gauge stays in the anti-slosh mode, which results in a slow to read full (F) event.The key ON fueling mode (approximately 90 seconds to read empty [E] to full [F]) requires the following conditions be met:

- Engine speed input greater than 0 rpm (late build only)
- The transaxle is in PARK (P) (automatic transaxles), or the parking brake applied (manual transaxles).
- The key is in the RUN position.
- At least 15% of the vehicle's fuel capacity must be added to the fuel tank.In key ON fueling mode, a 30-second timer activates after the transaxle put into the PARK (P) position (automatic transaxle) or when the parking brake is applied (manual transaxle). When the 30 second time has elapsed and at least 15% of the vehicle's fuel capacity has been added, the fuel gauge response time is 90 seconds to read from empty (E) to full (F). When the transaxle is shifted out of PARK (P) or the parking brake is released, the fuel gauge strategy reverts to the anti-slosh mode. The key ON fueling mode prevents slow to read full events from happening if the customer refuels the vehicle with the key in the RUN position.Recovery mode is incorporated into the instrument cluster strategy to recover from a missing fuel level input after a refueling event. Missing fuel level inputs result from intermittent opens in the fuel sender or its circuits. Recovery mode (empty [E] to full [F] approximately 20 minutes) is initiated when the following 2 conditions are met:

- The instrument cluster is in the anti-slosh (default) mode.
- The actual fuel level in the tank is greater than what is being displayed by the fuel gauge.

Instrument Cluster DTCs

B1202-B1204:

PCM DTCs

P0460-P0463:

Possible Causes
- Wiring, terminals or connectors
- Fuel tank
- Fuel level sender (float and card)
- Fuel pump module
- Instrument cluster

Diagnostic Procedure

CAUTION:Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

CAUTION:Following any fuel gauge repairs, remove fuse 26 (10A) for one minute then reinstall to reset the fuel gauge timers.

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