Part 3A
FUEL GAUGEA fuel gauge is standard equipment on all instrument clusters. The fuel gauge is located in the lower left quadrant of the instrument cluster, below the voltage gauge. The fuel gauge consists of a movable gauge needle or pointer controlled by the instrument cluster electronic circuitry and a fixed 90 degree scale on the cluster overlay that reads left-to-right from E (or Empty) to F (or Full). An International Control and Display Symbol icon for "Fuel" is located on the cluster overlay, in the center of the gauge directly above the hub of the gauge needle. An arrow head icon pointed toward the left side of the vehicle is imprinted on the cluster overlay next to the "Fuel" icon in the fuel gauge to provide the driver with a reminder as to the location of the fuel filler access. The fuel gauge graphics are white and blue against a black field except for a single red graduation at the low end of the gauge scale, making them clearly visible within the instrument cluster in daylight. When illuminated from behind by the panel lamps dimmer controlled cluster illumination lighting with the exterior lamps turned ON, the white graphics appear white, the blue graphics appear blue, and the red graphics appear red. The orange gauge needle is internally illuminated. Cluster illumination is provided by replaceable incandescent bulb and bulb holder units located on the instrument cluster electronic circuit board. The fuel gauge is serviced as a unit with the instrument cluster.
The fuel gauge gives an indication to the vehicle operator of the level of fuel in the fuel tank. This gauge is controlled by the instrument cluster electronic circuit board based upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus. The fuel gauge is an air core magnetic unit that receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or Start positions. The cluster is programmed to move the gauge needle back to the low end of the scale after the ignition switch is turned to the OFF position. The instrument cluster circuitry controls the gauge needle position and provides the following features:
- Percent Tank Full Message - Each time the cluster receives a message from the PCM indicating the percent tank full, the cluster programming applies an algorithm to calculate the proper gauge needle position, then moves the gauge needle to the proper position on the gauge scale. The algorithm is used to dampen gauge needle movement against the negative effect that fuel sloshing within the fuel tank can have on accurate inputs from the fuel tank sending unit to the PCM. The gauge needle will continue to be positioned at the proper position on the gauge scale until the cluster receives a message from the PCM that indicates the percent tank full is less than empty, more than full, or until the ignition switch is turned to the OFF position, whichever occurs first.
- Less Than 12.5 Percent Tank Full Message - Each time the cluster receives a message from the PCM indicating that the percent tank full is less than 12.5 (one-eighth), the gauge needle is moved to the proper position on the gauge scale, the low fuel indicator is illuminated, and a single chime tone is sounded. The low fuel indicator remains illuminated until the cluster receives messages from the PCM for a continuous 20 seconds indicating that the percent tank full has increased by more than 0.625 gallons or until the ignition switch is turned to the OFF position, whichever occurs first. This strategy is intended to reduce the effect that fuel sloshing within the fuel tank can have on reliable indications.
The chime tone feature will occur only once per ignition cycle.
- Less Than Empty Percent Tank Full Message - Each time the cluster receives a message from the PCM indicating that the percent tank full is less than empty, the gauge needle is moved to the far left (low) end of the gauge scale and the low fuel indicator is illuminated immediately. This message would indicate that the fuel tank sender input to the PCM is a short circuit.
- More Than Full Percent Tank Full Message - Each time the cluster receives a message from the PCM indicating the percent tank full is more than full, the gauge needle is moved to the far left (low) end of the gauge scale and the low fuel indicator is illuminated immediately. This message would indicate that the fuel tank sender input to the PCM is an open circuit.
- Message Failure - If the cluster fails to receive a percent tank full message, it will hold the gauge needle at the last indication for about 12 seconds, until a new message is received, or until the ignition switch is turned to the OFF position, whichever occurs first. After about 12 seconds, the gauge needle is moved to the far left (low) end of the gauge scale and the low fuel indicator is illuminated immediately.
- Actuator Test - Each time the cluster is put through the actuator test, the gauge needle will be swept to several calibration points on the gauge scale in a prescribed sequence to confirm the functionality of the gauge and the cluster control circuitry.
The PCM continually monitors the fuel tank sending unit, then sends the proper messages to the instrument cluster. For further diagnosis of the fuel gauge or the instrument cluster circuitry that controls the gauge, (Refer to ELECTRICAL / INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). For proper diagnosis of the fuel tank sending unit, the PCM, the PCI data bus, or the message inputs to the instrument cluster that control the fuel gauge, a DRB III scan tool is required. Refer to the appropriate diagnostic information.
HIGH BEAM INDICATOR
A high beam indicator is standard equipment on all instrument clusters. The high beam indicator is located near the upper edge of the instrument cluster overlay, between the tachometer and the speedometer. The high beam indicator consists of a stencil-like cutout of the International Control and Display Symbol icon for "High Beam" in the opaque layer of the instrument cluster overlay. The dark outer layer of the overlay prevents the indicator from being clearly visible when it is not illuminated. A blue lens behind the cutout in the opaque layer of the overlay causes the icon to appear in blue through the translucent outer layer of the overlay when it is illuminated from behind by a replaceable incandescent bulb and bulb holder unit located on the instrument cluster electronic circuit board. The high beam indicator is serviced as a unit with the instrument cluster.
The high beam indicator gives an indication to the vehicle operator when the headlamp high beams are illuminated, or when the exterior lamps are inadvertently left ON. This indicator is controlled by a hard wired input from the headlamp beam select switch circuitry of the left multi-function switch to the cluster, and by the instrument cluster electronic circuit board based upon cluster programming and hard wired inputs from the head/park/fog lamp switch circuitry of the left multi-function switch, the driver door ajar switch, and the ignition switch. The high beam indicator bulb is grounded on the instrument cluster electronic circuit board at all times; therefore, the bulb will be illuminated anytime the headlamp high beams are turned on, regardless of the ignition switch position. The bulb only illuminates when it is provided battery current by the beam select switch circuitry of the left multi-function switch, or by the instrument cluster electronic circuit board. The instrument cluster will turn on the high beam indicator for the following reasons:
- Beam Select Switch Input - Each time the cluster detects battery current on the beam select switch sense circuit (beam select switch closed = high beams selected or optical horn feature activated) the high beam indicator will be illuminated solid. This input can occur when the headlamp high beams are selected or when the optical horn feature is activated. The indicator remains illuminated until the beam select switch sense input to the cluster is an open circuit (beam select switch open = high beams not selected and optical horn feature not activated), or until the exterior lighting is turned OFF; whichever occurs first.
- Exterior Lamps-ON Optical Warning - Each time the cluster detects battery current on the headlamp switch output circuit (park or head lamp switch closed = exterior lighting is ON), ground on the driver door ajar switch sense circuit (driver door ajar switch closed = driver door is open), and the fused ignition switch output (Run-Start) input is an open circuit (ignition switch is in a position other than ON or Start), the high beam indicator will be flashed ON and OFF repeatedly. The indicator will continue to flash until the exterior lighting is turned OFF, the driver door is closed, or the ignition switch is turned to the ON or Start positions, whichever occurs first.
- Actuator Test - Each time the cluster is put through the actuator test, the high beam indicator will be turned ON, then OFF again during the bulb check portion of the test to confirm the functionality of the bulb and the cluster control circuitry.
The headlamp beam select switch and circuitry is integral to the left multi-function switch on the steering column, and is connected in series between fused B(+) and the high beam indicator driver circuit input to the instrument cluster. The left multi-function switch inputs to the instrument cluster circuitry can be diagnosed using conventional diagnostic tools and methods.(Refer to ELECTRICAL / LAMPS / LIGHTING - EXTERIOR / LEFT MULTI-FUNCTION SWITCH - OPERATION). For further diagnosis of the high beam indicator or the instrument cluster circuitry that controls the indicator bulb, (Refer to ELECTRICAL / INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING).
LOW FUEL INDICATOR
A low fuel indicator is standard equipment on all instrument clusters. The low fuel indicator is located near the lower edge of the instrument cluster overlay, to the left of the odometer/trip odometer Vacuum Fluorescent Display (VFD). The low fuel indicator consists of a stencil-like cutout of the International Control and Display Symbol icon for "Fuel" in the opaque layer of the instrument cluster overlay. The dark outer layer of the overlay prevents the indicator from being clearly visible when it is not illuminated. An amber lens behind the cutout in the opaque layer of the overlay causes the icon to appear in amber through the translucent outer layer of the overlay when it is illuminated from behind by a Light Emitting Diode (LED) soldered onto the instrument cluster electronic circuit board. The low fuel indicator is serviced as a unit with the instrument cluster.
The low fuel indicator gives an indication to the vehicle operator when the level of fuel in the fuel tank becomes low. This indicator is controlled by a transistor on the instrument cluster electronic circuit board based upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus. The low fuel indicator Light Emitting Diode (LED) receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or Start positions; therefore, the LED will always be OFF when the ignition switch is in any position except ON or Start. The LED only illuminates when it is provided a path to ground by the instrument cluster transistor. The instrument cluster will turn on the low fuel indicator for the following reasons:
- Bulb Test - Each time the ignition switch is turned to the ON position the low fuel indicator is illuminated for about two seconds as a bulb test.
- Less Than 12.5 Percent Tank Full Message - Each time the cluster receives a message from the PCM indicating that the percent tank full is less than 12.5 (one-eighth), the low fuel indicator is illuminated and a single chime tone is sounded. The low fuel indicator remains illuminated until the cluster receives messages from the PCM for a continuous 20 seconds indicating that the percent tank full has increased by more than 0.625 gallons or until the ignition switch is turned to the OFF position, whichever occurs first. This strategy is intended to reduce the effect that fuel sloshing within the fuel tank can have on reliable indications. The chime tone feature will occur only once per ignition cycle.
- Less Than Empty Percent Tank Full Message - Each time the cluster receives a message from the PCM indicating the percent tank full is less than empty, the low fuel indicator is illuminated immediately. This message would indicate that the fuel tank sender input to the PCM is a short circuit.
- More Than Full Percent Tank Full Message - Each time the cluster receives a message from the PCM indicating the percent tank full is more than full, the low fuel indicator is illuminated immediately. This message would indicate that the fuel tank sender input to the PCM is an open circuit.
- Actuator Test - Each time the cluster is put through the actuator test, the low fuel indicator will be turned ON, then OFF again during the bulb check portion of the test to confirm the functionality of the LED and the cluster control circuitry.
The PCM continually monitors the fuel tank sending unit, then sends the proper messages to the instrument cluster. For further diagnosis of the low fuel indicator lamp or the instrument cluster circuitry that controls the LED, (Refer to ELECTRICAL / INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). For proper diagnosis of the fuel tank sending unit, the PCM, the PCI data bus, or the message inputs to the instrument cluster that control the low fuel indicator, a DRB III scan tool is required. Refer to the appropriate diagnostic information.