Pinpoint Test B: Incorrect Fuel Gauge Indication
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test B: Incorrect Fuel Gauge Indication
Refer to Wiring Diagram Set 60, Instrument Cluster for schematic and connector information. Diagrams By Number
Normal Operation
The fuel tank is a saddle tank design with variable resistance senders in each side of the tank. The fuel pump module (LH side) and the fuel level sensor (RH side) are driven by floats that provide resistances related to the fuel level on each side of the tank to the Smart Junction Box (SJB). The fuel pump module and the fuel level sensor uses an approximate resistance range between 15 ohms ± 2 ohms at empty (E) and 160 ohms± 4 ohms at full (F). The fuel pump module is hardwired to the SJB through the signal circuit 1356 (LG/VT) and the return circuit 1357 (LB/YE). The fuel level sensor is hardwired to the SJB through the signal circuit 29 (YE/WH) and the return circuit 1357 (LB/YE). The SJB monitors the resistance readings that are sent to the SJB from the fuel pump module and the fuel level sensor and sends the Instrument Cluster (IC) a message over the communication network to command the fuel gauge with a corresponding movement of the pointer. If the fuel level sensor is open, the fuel gauge defaults to the fuel pump module value only and the fuel gauge indicates E to 1/2 tank. If the fuel pump module is open, the fuel gauge defaults to the empty position.
The IC uses 4 different operating modes to calculate the fuel level:
- Key OFF fueling
- Anti-slosh (default mode)
- 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.
Key OFF Fueling Mode
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 throughout the entire refueling of the vehicle.
- At least 15% of the vehicle's fuel capacity must be added to the fuel tank.
- The IC 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 15 ohms ± 2 ohms and 160 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.
Anti-Slosh Mode
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).
Key ON Fueling Mode
The key ON fueling mode (approximately 90 seconds to read empty [E] to full [F]) requires 3 conditions be met:
- The transmission is in PARK (P) (automatic transmissions), or the parking brake applied (manual transmissions).
- 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 transmission is placed into the PARK (P) position or when the parking brake is applied. 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 transmission 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
Recovery mode is incorporated into the IC strategy to recover from missing fuel level inputs during 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 IC 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.
B1202-B2879:
B1201-B2628:
P0460-P2068:
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Fuel pump module (LH side)
- Fuel level sensor (RH side)
- Fuel level sender (float and card)
- SJB
- Fuel tank
- IC
PINPOINT TEST B: INCORRECT FUEL GAUGE INDICATION
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
NOTE: Once the repairs are complete, clear the IC DTCs.
-------------------------------------------------
B1 CARRY OUT THE COMMUNICATION NETWORK TEST
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: Network Test.
- Carry out the network test.
- Does the SJB pass the network test?
Yes
GO to B2.
No
REFER to Information Bus.
-------------------------------------------------
B2 CARRY OUT THE IC FUEL GAUGE ACTIVE COMMAND USING THE SCAN TOOL
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: IC Active Command.
- Select the IC fuel level control active command and scroll the fuel level at: 0%, 50%, and 100%.
- Does the fuel gauge needle start at empty (E), move to half at 50%, and full (F) at 100%?
Yes
GO to B3.
No
GO to B23.
-------------------------------------------------
B3 RETRIEVE THE RECORDED DTCs FROM THE CONTINUOUS MEMORY IC SELF-TEST
NOTE: The IC DTCs are all set in continuous memory only. For all diagnostics, use only the IC DTCs.
- Check for recorded continuous memory IC DTCs from the self-test.
- Are any IC DTCs recorded?
Yes
For DTC B1204 or DTC B2628, GO to B4.
For DTC B1202, GO to B8.
For DTC B2627, GO to B13.
For DTC B2879, GO to B18.
No
GO to B18.
-------------------------------------------------
B4 CHECK THE FUEL SENDER FOR A SHORT TO GROUND
NOTE: The fuel pump module may also be called the fuel tank unit.
NOTE: The fuel level sensor may also be called the fuel sender.
- Disconnect: Fuel Pump Module C433 (4.0L and 4.6L) or C4331 (5.4L) (DTC B1204) (LH Side) or Fuel Sender C434 (DTC B2628) (RH Side).
- Ignition ON.
- Wait one minute.
- Enter the following diagnostic mode on the scan tool: IC Self-Test.
- NOTE: Make sure to use only the IC DTCs for this step. Once the repairs are complete, clear the IC DTCs.
- NOTE: It is normal for DTC B1204 or B2628 to be present during this step and should be ignored.
- Clear the IC DTCs. Repeat the IC self-test.
- Is DTC B1202 or B2627 retrieved?
Yes
To continue DTC B1204 diagnostics, GO to B21.
To continue DTC B2628 diagnostics, INSTALL a new fuel level sensor. CLEAR the DTCs. REPEAT the self-test.
No
GO to B5.
-------------------------------------------------
B5 CHECK CIRCUITS 29 (YE/WH) OR 1356 (LG/VT) FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: SJB C2280c.
- For DTC B2628, measure the resistance between the SJB C2280c-43, circuit 29 (YE/WH) (DTC B2628), harness side and ground
- For DTC B1204, measure the resistance between the SJB C2280c-44, circuit 1356 (LG/VT) (DTC B1204), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
For DTC B1204, GO to B6.
For DTC B2628, GO to B7.
No
REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------
B6 CHECK CIRCUITS 1356 (LG/VT) AND 1357 (LB/YE) FOR A SHORT TOGETHER
- Measure the resistance between the SJB C2280c-31, circuit 1357 (LB/YE), harness side and the SJB C2280c-44, circuit 1356 (LG/VT), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to B22.
No
REPAIR the circuits. CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------
B7 CHECK CIRCUITS 29 (YE/WH) AND 1357 (LB/YE) FOR A SHORT TOGETHER
- Measure the resistance between the SJB C2280c-43, circuit 29 (YE/WH), harness side and the SJB C2280c-31, circuit 1357 (LB/YE), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to B22.
No
REPAIR the circuits. CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------
B8 CHECK THE FUEL PUMP MODULE FOR AN OPEN
- Ignition OFF.
- Disconnect: Fuel Pump Module C433 (4.0L and 4.6L) or C4331 (5.4L) (LH Side).
- On 4.0L and 4.6L engines, connect a fused jumper wire between the fuel pump module C433-2, circuit 1357 (LB/YE), harness side and the fuel pump module C433-4, circuit 1356 (LG/VT), harness side.
- On 5.4L engines, connect a fused jumper wire between the fuel pump module C4331-2, circuit 1357 (LB/YE), harness side and the fuel pump module C4331-5, circuit 1356 (LG/VT), harness side.
- Ignition ON.
- Wait one minute.
- Enter the following diagnostic mode on the scan tool: IC Self-Test.
- NOTE: Make sure to use only the IC DTCs for this step. Once the repairs are complete, clear the IC DTCs.
- NOTE: It is normal for DTC B1202 to be present during this step and should be ignored.
- Clear the IC DTCs. Repeat the IC self-test.
- Is DTC B1204 set?
Yes
REMOVE the jumper wire. GO to B21.
No
LEAVE the jumper wire connected. GO to B9.
-------------------------------------------------
B9 CHECK THE FUEL PUMP MODULE CIRCUITRY FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: SJB C2280c.
- Ignition ON.
- Measure the voltage between the SJB C2280c-44, circuit 1356 (LG/VT), harness side and ground.
- Is any voltage present?
Yes
REMOVE the jumper wire. GO to B10.
No
LEAVE the jumper wire connected. GO to B11.
-------------------------------------------------
B10 CHECK CIRCUIT 1356 (LG/VT) FOR A SHORT TO VOLTAGE
- Measure the voltage between the SJB C2280c-44, circuit 1356 (LG/VT), harness side and ground.
- Is any voltage present?
Yes
REPAIR circuit 1356 (LG/VT) for a short to voltage. CLEAR the DTCs. REPEAT the self-test.
No
REPAIR circuit 1357 (LB/YE) for a short to voltage. CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------
B11 CHECK THE FUEL PUMP MODULE CIRCUITRY FOR AN OPEN
- Ignition OFF.
- Measure the resistance between the SJB C2280c-31, circuit 1357 (LB/YE), harness side; and between the SJB C2280c-44, circuit 1356 (LG/VT), harness side.
- Is the resistance less than 5 ohms?
Yes
REMOVE the jumper wire. GO to B22.
No
REMOVE the jumper wire. GO to B12.
-------------------------------------------------
B12 CHECK CIRCUIT 1356 (LG/VT) FOR AN OPEN
- On 4.0L and 4.6L engines, measure the resistance between the SJB C2280c-44, circuit 1356 (LG/WH), harness side and the fuel pump module C433-4, circuit 1356 (LG/WH), harness side.
- On 5.4L engines, measure the resistance between the SJB C2280c-44, circuit 1356 (LG/WH), harness side and the fuel pump module C4331-5, circuit 1356 (LG/WH), harness side.
- Is the resistance less than 5 ohms?
Yes
REPAIR circuit 1357 (LB/YE) for an open. CLEAR the DTCs. REPEAT the self-test.
No
REPAIR circuit 1356 (LG/WH) for an open. CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------
B13 CHECK THE FUEL LEVEL SENSOR FOR AN OPEN
- Ignition OFF.
- Disconnect: Fuel Level Sensor C434 (RH Side).
- Connect a fused jumper wire between the fuel level sensor C434-4, circuit 29 (LB/YE), harness side and the fuel level sensor C434-2, circuit 1356 (LG/VT), harness side.
- Ignition ON.
- Wait one minute.
- Enter the following diagnostic mode on the scan tool: IC Self-Test.
- NOTE: Make sure to use only the IC DTCs for this step. Once the repairs are complete, clear the IC DTCs.
- NOTE: It is normal for DTC B2627 to be present during this step and should be ignored.
- Clear the IC DTCs. Repeat the IC self-test.
- Is DTC B2628 set?
Yes
INSTALL a new fuel level sensor. CLEAR the DTCs. REPEAT the self-test.
No
LEAVE the jumper wire connected. GO to B14.
-------------------------------------------------
B14 CHECK CIRCUIT 29 (YE/WH) FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: SJB C2280c.
- Ignition ON.
- Measure the voltage between the SJB C2280c-43, circuit 29 (YE/WH), harness side and ground.
- Is any voltage present?
Yes
REMOVE the jumper wire. GO to B15.
No
LEAVE the jumper wire connected. GO to B16.
-------------------------------------------------
B15 CHECK CIRCUIT 29 (YE/WH) FOR A SHORT TO VOLTAGE WITH THE CIRCUIT ISOLATED
- Measure the voltage between the SJB C2280c-43, circuit 29 (YE/WH), harness side and ground.
- Is any voltage present?
Yes
REPAIR circuit 29 (YE/WH) for a short to voltage. CLEAR the DTCs. REPEAT the self-test.
No
REPAIR circuit 1357 (LB/YE) for a short to voltage. CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------
B16 CHECK THE FUEL LEVEL SENSOR CIRCUITRY FOR AN OPEN
- Ignition OFF.
- Measure the resistance between the SJB C2280c-31, circuit 1357 (LB/YE), harness side; and between the SJB C2280c-43, circuit 29 (YE/WH), harness side.
- Is the resistance less than 5 ohms?
Yes
REMOVE the jumper wire. GO to B22.
No
REMOVE the jumper wire. GO to B17.
-------------------------------------------------
B17 CHECK CIRCUIT 29 (YE/WH) FOR AN OPEN
- Measure the resistance between the SJBC2280c-43, circuit 29 (YE/WH), harness side and the fuel level sensor C434-4, circuit 29 (YE/WH), harness side.
- Is the resistance less than 5 ohms?
Yes
REPAIR circuit 1357 (LB/YE) for an open. CLEAR the DTCs. REPEAT the self-test.
No
REPAIR circuit 29 (YE/WH) for an open. CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------
B18 INSPECT THE FUEL TANK
- Check the fuel tank for any damage or deformation.
- Is the fuel tank OK?
Yes
GO to B19.
No
VERIFY that the fuel pump module or fuel level sensor are not damaged. INSTALL a new fuel tank. CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------
B19 INSPECT THE FUEL PUMP MODULE, FUEL LEVEL SENSOR AND FUEL TRANSFER TUBES
- Remove the fuel pump module and fuel level sensor.
- Inspect the fuel transfer tube, connections, fuel pump module and fuel level sensor for any damage or deformation.
- Are the fuel transfer tube, connections, fuel pump module and the fuel level sensor OK?
Yes
GO to B20.
No
REPAIR or INSTALL a new fuel tank (for fuel transfer tube concerns), fuel pump module or fuel level sensor as necessary. CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------
B20 CHECK THE FUEL PUMP MODULE AND FUEL LEVEL SENSOR RESISTANCE READINGS
NOTE: The fuel pump module and fuel level sensor resistance varies from 15 ± 2 ohms when empty (E) to 160 ± 4 ohms when full (F).
- On 4.0L and 4.6L engines, measure the resistance between the fuel pump module C433 pin 2, component side and the fuel pump module C433 pin 4, component side.
- On 5.4L engines, measure the resistance between the fuel pump module C4331 pin 2, component side and the fuel pump module C4331 pin 5, component side.
- For all engines, measure the resistance between the fuel level sensor C434 pin 4, component side and the fuel level sensor C434 pin 2, component side while slowly moving the float arm from the bottom to the top of travel.
- Does the resistance of both senders start at approximately 15 ohms with the float at the bottom of the travel and slowly increase to approximately 160 ohms with the float at the top of the travel?
Yes
INSTALL a new fuel tank. CLEAR the DTCs. REPEAT the self-test.
No
For the fuel pump module, GO to B21.
For the fuel level sensor, INSTALL a new fuel level sensor. CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------
B21 CHECK THE FUEL LEVEL SENDER
- NOTE: The fuel level sender resistance will measure between 15 ohms ± 2 ohms at the lower stop position and 160 ohms ± 4 ohms at the upper stop position.
- Remove the fuel pump module.
- NOTE: Disconnect the fuel level sender input wire from the fuel level sender for this measurement.
- Measure the resistance between the fuel level sender input wire and the fuel level sender ground while slowly moving the float arm between the lower stop and the upper stop position.
- Does the resistance slowly increase from approximately 15 ohms to 160 ohms?
Yes
INSTALL a new fuel pump module. TEST the system for normal operation.
No
INSTALL a new fuel level sender. TEST the system for normal operation.
-------------------------------------------------
B22 CHECK FOR CORRECT SJB OPERATION
- Disconnect all the SJB connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the SJB connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new SJB. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------
B23 CHECK FOR CORRECT IC OPERATION
- Disconnect the IC connector.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect the IC connector and make sure it seats correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------