The CHECK GAUGES indicator lamp lights when either the engine oil pressure is at or below approximately 34 kPa (5 psi) or whenever the engine coolant temperature is at or over approximately 118°C (245°F), as sent from the malfunction alarm module. The ignition switch must be in the RUN position in order to power the CHECK GAUGES lamp driver. Circuit Breaker #6 in the IP fuse block provides power to the lamp. The lamp driver is grounded by the multifunction alarm module. The CHECK GAUGES indicator lamp remains lit after the engine is started until the engine oil pressure exceeds the low oil pressure setpoint.

Battery voltage, from circuit breaker #6 in the IP fuse block, powers the oil pressure gauge when the ignition switch is in the RUN position. If the current through the oil pressure gauge and the oil pressure sensing element is high, the pointer moves toward the 0 kPa (0 psi) indication. If the current through the gauge and the sensor decreases, the gauge moves toward the 550 kPa (80 psi) indication.

The current that passes through the oil pressure gauge passes through two magnetic coils. The vertical coil connects directly to ground. The horizontal coil ground path passes through the oil pressure sensing element. Some of the current always passes through the vertical coil. The percentage of total current passing through the horizontal coil depends on the resistance of the oil pressure sensing element. The oil pressure sensing element produces a resistance of approximately 0 ohms when the oil pressure is zero. The oil pressure sensing element produces a resistance of approximately 88 ohms when the oil pressure is at 550 kPa (80 psi). With a lower resistance, a greater percentage of the total current passes through the horizontal coil and the pointer moves to 0 kPa (0 psi). When the oil pressure is high, a smaller percentage of the current flows through the oil pressure gauge horizontal coil and the pointer moves toward 550 kPa (80 psi).

When the multifunction alarm module senses a high temperature, (low oil pressure) condition, the multifunction alarm module grounds the CHECK GAUGES cluster indicator lamp input terminal, B8. The oil pressure setpoint is at approximately 34 kPa (5 psi).

The accuracy of the oil pressure gauge is adequate for normal operator usage because the oil pressure gauge provides a reasonably accurate indication of the engine oil pressure from which sudden or long term changes may be identified. The response of the sensing element is essentially linear over the operating range. The gauge accuracy is for 3.5 degrees (angular) at 0 kPa (80 psi) and for 7 degrees at 550 kPa (80 psi). Changes in the battery voltage do not affect the gauge accuracy.

The speedometer and the odometer operate through solid state circuity inside the instrument cluster. The IP fuse block circuit breaker #6 powers the instrument cluster through CKT 41 (BRN). The instrument cluster receives a square wave, 4,000 pulses per mile signal from the vehicle speed sensor (VSS) buffer through CKT 42 and CKT 422 (WHT). The solid state electronics position the speedometer pointer in response to the pulse rate. The electronics also drive the odometer indication in response to the pulse rate over time.

The speedometer's rated accuracy at 65 mph is plus or minus 2 mph (63 to 67 mph). At 20 mph, the rated accuracy is plus or minus 4 mph (16 to 24 mph). Variations in voltage and inaccuracies in the other circuit components may increase the error.

The timing and injection rate control system (TICS) module drives the tachometer. The TICS module receives the input from the engine speed sensor and generates the tachometer output signal which is sent to the cluster mounted tachometer.

The magnetic fields of the two coils, the 38°C (100°F) coil and the 126°C (260°F) coil, moves the pointer of the temperature gauge. The two coils are oriented at right angles so that the magnetic fields interfere with each other. When the ignition switch is in the RUN position, circuit breaker #6 makes battery voltage available to the instrument cluster through CKT 21, CKT 28, CKT 1 or CKT 371 (BRN). If little current flows through the 126°C (260°F) coil, then current flows through the 38°C (100°F) coil which places the pointer at 38°C (100°F), low temperature. If the current through the 126°C (260°F) coil is high, then the pointer moves toward the 126°C (260°F), high temperature, indication.

The current that passes through the 126°C (260°F) coil has two paths to ground. Some of the current can pass through the fixed resistance of the 38°C (100°F) coil and to G101 through CKT 451 (BLK/WHT). The remainder of the current passes to ground through the variable resistance of the temperature sensor. The engine coolant temperature gauge sensor produces a resistance of approximately 1,305 ohms when the temperature is 38°C (100°F). With this high resistance, more current flows through the 38°C (100°F) coil and the pointer moves toward 38°C (100°F). The resistance of the sensor is approximately 61.9 ohms at 118°C (245°F). With this low resistance, more current passes through the temperature sensor and not the 38°C (100°F) coil. The pointer moves toward 126°C (260°F).

When the multifunction alarm module senses a high temperature (low oil pressure) condition the MFAM grounds the CHECK GAUGES indicator lamp input terminal, B8. The temperature setpoint is at approximately 61.9 Ohms or 245°F (118°C).

The accuracy of the temperature gauge is adequate for the normal operator usage because the temperature gauge provides a reasonably accurate indication of the engine coolant temperature from which sudden or long term changes may be identified. The response of the sensing element is non-linear over the operating range. This condition limits accuracy. The gauge accuracy specification is for 3.5 degrees (angular) at 126°C (260°F) and for 7 degrees at 38°C (100°F). Changes in the battery voltage do not affect the gauge accuracy.

The voltmeter indicates battery voltage when the ignition switch is in the RUN position. The voltmeter measures generator voltage when the engine is running. The normal generator voltage is 14 volts. The battery voltage without the engine running depends upon the ambient temperature. The battery voltage may be as low as 9.6 volts. Circuit breaker #6 supplies voltage to the voltmeter through CKT 26), CKT 1 or CKT 371 (BRN). Ground for the single coil indicator passes through CKT 27 (BLK) to joint connector #1 (upper).