Part 4B
TACHOMETERA tachometer is standard equipment on all instrument clusters. The tachometer is located next to the speedometer, just to the left of center in the instrument cluster. The tachometer consists of a movable gauge needle or pointer controlled by the instrument cluster electronic circuitry and a fixed 210 degree scale on the cluster overlay that reads left-to-right from 0 to 6. The text "X 1000 RPM" imprinted on the cluster overlay directly below the hub of the tachometer needle identifies that each number on the tachometer scale is to be multiplied by 1000 rpm. A red line on the high end of the gauge scale designates the engine overspeed area of the gauge. The tachometer graphics are white against a black field, except for the single red line, 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 and the red graphics appear red. The orange gauge needle is internally illuminated. Gauge illumination is provided by replaceable incandescent bulb and bulb holder units located on the instrument cluster electronic circuit board. The tachometer is serviced as a unit with the instrument cluster.
The tachometer gives an indication to the vehicle operator of the engine speed. 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 tachometer 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 electronic circuitry controls the gauge needle position and provides the following features:
- Engine Speed Message - Each time the cluster receives an engine speed message from the PCM it will calculate the correct engine speed reading and position the gauge needle at that speed position on the gauge scale. The cluster will receive a new engine speed message and reposition the gauge pointer accordingly about every 86 milliseconds. The gauge needle will continue to be positioned at the actual engine speed position on the gauge scale until the ignition switch is turned to the OFF position.
- Message Failure - If the cluster fails to receive an engine speed message, it will hold the gauge needle at the last indication for about six seconds, or until the ignition switch is turned to the OFF position, whichever occurs first. If a new engine speed message is not received after about six seconds, the gauge needle will return to the far left (low) end of the scale.
- 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 crankshaft position sensor to determine the engine speed, then sends the proper engine speed messages to the instrument cluster. For further diagnosis of the tachometer or the instrument cluster circuitry that controls the gauge, (Refer to ELECTRICAL / INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). For proper diagnosis of the crankshaft position sensor, the PCM, the PCI data bus, or the message inputs to the instrument cluster that control the tachometer, a DRB III scan tool is required. Refer to the appropriate diagnostic information.
TURN SIGNAL INDICATOR
Two turn signal indicators, one right and one left, are standard equipment on all instrument clusters. The turn signal indicators are located near the upper edge of the instrument cluster overlay, between the speedometer and the tachometer. Each turn signal indicator consists of a stencil-like cutout of the International Control and Display Symbol icon for "Turn Warning" in the opaque layer of the instrument cluster overlay. The dark outer layer of the overlay prevents these icons from being clearly visible when they are not illuminated. A green lens behind each cutout in the opaque layer of the cluster overlay causes the indicator to appear in green 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 turn signal indicators are serviced as a unit with the instrument cluster.
The turn signal indicators give an indication to the vehicle operator that the turn signal (left or right indicator flashing) or hazard warning (both left and right indicators flashing) have been selected. These indicators are controlled by two individual hard wired inputs from the turn signal switch and hazard warning switch circuitry of the left multi-function switch to the cluster. Each turn signal indicator Light Emitting Diode (LED) is grounded on the instrument cluster electronic circuit board at all times; therefore, the LED can be on anytime the turn signal or hazard warning systems are turned on, regardless of the ignition switch position. Each LED will only illuminate when it is provided battery current by the turn signal switch or hazard warning switch circuitry of the left multi-function switch.
The turn signal switch and hazard warning switch circuitry of the left multi-function switch are connected in series between the output of the combination flasher on the left multi-function switch and the left or right turn signal inputs to the instrument cluster, but in parallel with the other turn signal circuits. This arrangement allows the turn signal indicators to remain functional, regardless of the condition of the other circuits in the turn signal and hazard warning systems. The turn signal switch and hazard warning switch inputs to the instrument cluster can be diagnosed using conventional diagnostic tools and methods. (Refer to ELECTRICAL/ LAMPS/LIGHTING - EXTERIOR/LEFT MULTI- FUNCTION SWITCH - OPERATION) for more information on the turn signal switch and hazard warning switch.
UPSHIFT INDICATOR
An upshift indicator is standard equipment on all instrument clusters, however, on vehicles not built for the United States or Canadian markets and those not equipped with a manual transmission, this indicator is electronically disabled. The upshift indicator is located near the right upper edge of the instrument cluster overlay, just above the oil pressure gauge. The upshift indicator consists of an upward pointed arrow icon that is a stencil-like cutout in the opaque layer of the instrument cluster overlay. The dark outer layer of the cluster overlay prevents the icon from being clearly visible when the lamp is not illuminated. An amber lens behind the cutout in the opaque layer of the cluster 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. When the exterior lighting is turned ON, the illumination intensity of the part time indicator is one-step dimmable, which is adjusted using the panel lamps dimmer control ring on the left multi-function switch control stalk. The upshift indicator is serviced as a unit with the instrument cluster.
The upshift indicator gives an indication to the vehicle operator when the manual transmission should be shifted to the next highest gear in order to achieve the best fuel economy. 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 upshift indicator function of the instrument cluster is electronically enabled or disabled by a PCI data bus message received by the cluster from the PCM. The upshift 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 indicator 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 upshift indicator for the following reasons:
- Upshift Lamp-ON Message - Each time the cluster receives an upshift lamp-ON message from the PCM indicating the engine speed and load conditions are right for a transmission upshift to occur, the upshift indicator is illuminated. The indicator remains illuminated until the cluster receives an upshift lamp-OFF message from the PCM or until the ignition switch is turned to the OFF position, whichever occurs first. The PCM will normally send an upshift lamp-OFF message three to five seconds after a lamp-ON message, if an upshift is not performed. The indicator will then remain OFF until the vehicle stops accelerating and is brought back into the range of indicator operation, or until the transmission is shifted into another gear.
- Actuator Test - Each time the cluster is put through the actuator test, the upshift 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 engine speed and load conditions to determine the proper fuel and ignition requirements. The PCM then sends the proper upshift indicator messages to the instrument cluster. For further diagnosis of the upshift indicator or the instrument cluster circuitry that controls the indication (Refer to ELECTRICAL / INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). For proper diagnosis of the PCM, the PCI data bus, or the message inputs to the instrument cluster that control the upshift indicator, a DRB III scan tool is required. Refer to the appropriate diagnostic information.
VOLTAGE GAUGE
A voltage gauge is standard equipment on all instrument clusters. The voltage gauge is located in the upper left quadrant of the instrument cluster, above the fuel gauge. The voltage 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 9 volts to 19 volts. An International Control and Display Symbol icon for "Battery Charging Condition" is located on the cluster overlay, in the center of the gauge directly above the hub of the gauge needle. The voltage gauge graphics are white and blue against a black field except for a single red graduation at each 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. Gauge illumination is provided by replaceable incandescent bulb and bulb holder units located on the instrument cluster electronic circuit board. The voltage gauge is serviced as a unit with the instrument cluster.
The voltage gauge gives an indication to the vehicle operator of the electrical system voltage. 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 voltage 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:
- System Voltage Message - Each time the cluster receives a message from the PCM indicating the system voltage, the gauge needle is moved to the actual system voltage position on the gauge scale. The gauge needle will continue to be positioned at the actual system voltage position on the gauge scale until the cluster receives a message from the PCM that indicates the system voltage is low (charge fail), high, or until the ignition switch is turned to the OFF position, whichever occurs first.
- Charge Fail Message - Each time the cluster receives a message from the PCM indicating a charge fail condition (system voltage is nine volts or lower), the gauge needle is moved to the 9 volt graduation on the gauge scale and the check gauges indicator is illuminated. The gauge needle remains on the 9 volt graduation and the check gauges indicator remains illuminated until the cluster receives a message from the PCM indicating there is no charge fail condition (system voltage is 12 volts or higher, but lower than 16 volts), or until the ignition switch is turned to the OFF position, whichever occurs first.
- Voltage High Message - Each time the cluster receives a message from the PCM indicating a voltage high condition (system voltage is 19 volts or higher), the gauge needle is moved to the 19 volt graduation on the gauge scale and the check gauges indicator is illuminated. The gauge needle remains on the 19 volt graduation and the check gauges indicator remains illuminated until the cluster receives a message from the PCM indicating there is no voltage high condition (system voltage is 16 volts or lower, but higher than nine volts), or until the ignition switch is turned to the OFF position, whichever occurs first.
- Message Failure - If the cluster fails to receive a system voltage message for more than about 12 seconds, it will move the gauge needle to the minimum graduation of the gauge scale until a new message is received, or until the ignition switch is turned to the OFF position, whichever occurs first.
- 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 system voltage to control the generator output. The PCM then sends the proper system voltage messages to the instrument cluster. For further diagnosis of the voltage gauge or the instrument cluster circuitry that controls the gauge, (Refer to ELECTRICAL / INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). If the instrument cluster turns on the check gauges indicator due to a charge fail or voltage high condition, it may indicate that the charging system requires service. For proper diagnosis of the charging system, the PCI data bus, or the message inputs to the instrument cluster that control the voltage gauge, a DRB III scan tool is required. Refer to the appropriate diagnostic information.