Description & Operation
The analog instrument cluster contains: speedometer/odometer, tachometer (if equipped), fuel gauge, temperature gauge and warning lights placed in various locations around instrument cluster. See Fig 1.
Vehicle options determine which of the warning indicators are operational. Although instrument panel may be equipped with an indicator it may not apply to this vehicle. Gauges and warning indicators may use outputs from common sensors to carry out their respective functions. Sensor functions should be considered when diagnosing a problem with any instruments and warning indicators. Instrument clusters should be replaced as an assembly and not dismantled for repair.
The speedometer, odometer, tachometer and temperature gauge receives information from the Powertrain Control Module (PCM) over Standard Corporate Protocol (SCP) network. When speedometer does not receive a vehicle speed signal, the display defaults to 0.0 MPH (0.0 km/h). The odometer records total vehicle mileage and is equipped with a trip meter that can be reset by pushing a button. If odometer does not receive information from the PCM, the display will show all dashes. The temperature gauge will default to COLD position if information from PCM is missing or invalid. The Malfunction Indicator Light (MIL) illuminates if a Diagnostic Trouble Code (DTC) is received from PCM which affects exhaust emissions. The powertrain warning indicator illuminates when a DTC is registered in the PCM that does not affect exhaust emissions or if vehicle goes into cooling system fail-safe mode. Other PCM outputs are the shift up indicator which informs driver when to change gears and charge system warning indicator, which illuminates when engine is off and if PCM detects a problem in charging system circuit.
The safety belt warning Indicator is activated by the Central Timer Module (CTM) when driver seat belt is not fastened. The indicator will go out automatically after 60 seconds even if safety belt has not been fastened. The door ajar indicator is activated by CTM and anti-theft warning module. The door ajar indicator will illuminate when a ground signal is received from a door, liftgate or trunk switch.
The fuel gauge and low fuel warning indicator receives information from fuel sending unit, which is a variable resistor that varies ground supply to the gauge and is part of the fuel pump module. Fuel level input is heavily dampened to allow movement of fuel in tank, and reads when ignition switch is in RUN position. If an invalid signal is received, gauge will default to below EMPTY position. The low fuel warning indicator illuminates when fuel drops to a pre-determined level.
The Anti-lock Brake System (ABS) warning light is hardwired directly to ABS module. ABS warning light should come on for 30 seconds and go out (prove out) after ignition is switched to RUN position. A short to battery, open circuit or ABS failure will illuminate ABS warning indicator. The brake warning indicator will illuminate if brake fluid is low or parking brake is set. When ignition switch is set to RUN position, the brake warning indicator grounds the circuit and runs the self-test. The engine oil pressure warning indicator receives its ground from the engine oil pressure sending unit mounted on engine. The oil pressure warning indicator illuminates when ignition is in RUN position. When engine develops oil pressure the circuit to ground opens, turning out the oil pressure warning indicator light. Turn signal and high beam indicators receive voltage directly from their switches. Indicators illuminate when headlight high beam or turn signal light is illuminated.