GM Service Manual Online
For 1990-2009 cars only
ABS System Disable: This parameter displays Yes if the PCM is not receiving input from the Antilock Brake System (ABS), and the AWD system is disabled.

AWD Circuit Status: The All Wheel Drive (AWD) Circuit Status parameter indicates the status of the Axle Actuator Control Circuit to the AWD solenoid and displays OK, Short or Open. The PCM can detect a short to ground, a short to power, or an open in the Axle Actuator Control Circuit. The AWD Disabled lamp will be illuminated for a short and open conditions.

AWD Clutch Temp. Disable: The All Wheel Drive (AWD) Clutch Temperature Disable parameter displays the status of powertrain software that has the ability to disable AWD based on a rear drive module clutch slip/time calculation and displays Yes or No. If the software determines that a clutch overtemperature condition exists, the PCM will deactivate the AWD system by disabling the PWM signal line to the AWD solenoid. The AWD system will be enabled again when the software calculates that the clutch temperatures have dropped sufficiently. The AWD Disabled lamp will be illuminated for a Yes condition.

AWD Disabled: The All Wheel Drive (AWD) Disabled parameter indicates if the AWD system has been disabled by the PCM and displays Yes or No. The AWD Disabled lamp will be illuminated for a Yes condition.

AWD Duty Cycle: The All Wheel Drive (AWD) Duty Cycle parameter displays the commanded state of the AWD solenoid expressed as a percent of ON time. At vehicle start-up, duty cycle will be at 75-90% for 3 seconds. This is referred to as the pull-in duty cycle. After 3 seconds the duty cycle will drop to 20-30% for 30 seconds. This is referred to as the hold-in duty cycle. After each 30 second hold-in period, the duty cycle will be increased to 75-90%, pull-in duty cycle, for 0.5 second before returning to the hold-in duty cycle. This is to assure solenoid pull-in.

AWD Fluid Temp. Disable: The All Wheel Drive (AWD) Fluid Temperature Disable parameter indicates a fluid overtemperature condition in the rear drive module and displays Yes or No. When the sump temperature exceeds approximately 110°C (230°F), a pull-up resistor grounds the PWM signal line from the PCM at the AWD solenoid. The pull-up resistor is an integral part of the AWD solenoid. The AWD Disabled lamp will be illuminated for a Yes condition.

AWD Minispare Disable: The All Wheel Drive (AWD) Minispare Disable parameter indicates whether the ABS module detects a mini spare on the vehicle and displays Yes or No. The wheel rotational speed difference is detected by the wheel speed sensors of the ABS system. If the ABS module detects a minispare on the vehicle, the PCM will deactivate the AWD system by disabling the PWM signal line to the AWD solenoid. The AWD Disabled lamp will be illuminated for a Yes condition.

AWD Overtemp. Delay: The All Wheel Drive (AWD) Overtemperature Delay parameter indicates whether the AWD system is in a reset mode following an AWD fluid temperature disable and displays Yes or No. There is a 10 minute delay from the time the rear drive module resistor closes the PWM signal line until the PCM again checks the signal line for an overtemperature condition. The rear drive module resistor is an integral part of the AWD solenoid. The AWD Disabled lamp will be illuminated for a Yes condition.

AWD Torque Management: The All Wheel Drive (AWD) Torque Management parameter indicates when some form of torque management is being performed to protect the AWD system and displays Active. When there is no form of torque management being performed the display reads Inactive.

AWD Voltage Disable: The All Wheel Drive (AWD) Voltage Disable parameter indicates whether the ignition voltage to the AWD solenoid is in the proper range and displays Yes or No. The ignition voltage range to the AWD solenoid is 9-16 volts. The PCM will deactivate the AWD system by disabling the PWM signal line to the AWD solenoid if the ignition voltage is out of range. The AWD Disabled lamp will be illuminated for a Yes condition.

AWD Wheel Speed Disable: The All Wheel Drive (AWD) Wheel Speed Disable parameter indicates whether the wheel speed data received from the ABS controller is valid and displays Yes or No. If the ABS module transmits it is not OK for the AWD system to be active, the PCM will deactivate the AWD system by disabling the PWM signal line to the AWD solenoid. The AWD Disabled lamp will be illuminated for a Yes condition.

Commanded Gear: This parameter indicates the current commanded state of the shift solenoid valves.

ECT: The Engine Coolant Temperature (ECT) sensor is mounted in the coolant stream and sends engine temperature information to the PCM. The PCM applies 5 volts to the ECT sensor circuit. The sensor is a thermistor that changes internal resistance as temperature changes. When the sensor is cold, the internal resistance is high, the PCM monitors a high signal voltage. The PCM interprets this voltage as a cold engine. As the sensor warms, the internal resistance decreases, the voltage signal will decrease. The PCM interprets the lower voltage as a warm engine.

Engine Speed: This parameter indicates the rotational speed of the engine expressed as revolutions per minute. The engine speed is computed by the PCM from the fuel control reference input, the crankshaft position sensor.

Engine Torque: This parameter indicates the amount of torque being delivered by the engine and is displayed in both English and metric units.

Gear Ratio: This parameter displays the actual transmission gear ratio as the transmission operates through all DRIVE, REVERSE and PARK/NEUTRAL ranges.

Ignition Voltage: This parameter is the system voltage measured by the PCM at the PCM ignition input when the ignition switch is in the RUN position.

IMS: The Internal Mode Switch (IMS) parameter displays Park, Park/Reverse, Reverse, Reverse/Neutral, Neutral, Neutral/Drive 4, Drive 4, Drive 4/Drive 3, Drive 3, Drive 3/Drive 2, Drive 2, Drive 2/Drive 1, Drive 1, Invalid or Open. The IMS Range display represents a decoded status of the four inputs from the IMS. This range includes all possible in-between gear states as well as the detent gear states. The combination of IMS inputs to the PCM are used by the PCM in order to determine the position of the manual valve at any given time.

IMS A/B/C/P: The Internal Mode Switch (IMS) A/B/C/P parameter displays LOW or HI for the state of each of the four inputs from the IMS. LOW displayed indicates a low voltage signal, 0 volts, being monitored at the PCM. HI displayed indicates a high voltage signal, B+, being monitored at the PCM.

Last Disable Odometer: This parameter indicates the vehicle mileage at which the AWD Last Disable condition occurred.

Last Disable Reason: This parameter indicates the last AWD disable reason. The possible reasons are Output Controls, Fluid Temp, Clutch Temp, Wheel Speed, Voltage, Mini Spare, ABS System. The Output Controls reason indicates that AWD was last disabled with a service scan tool. Fluid Temp, Clutch Temp, Wheel Speed, Voltage, Mini Spare and ABS System each have a unique parameter that is described elsewhere in this table.

TP Angle: The Throttle Position (TP) Angle parameter displays a percentage that is computed by the PCM from the TP sensor voltage. The TP angle should display 0% at idle and 100% at wide open throttle (WOT).

Trans. Fluid Temp.: The Transmission Fluid Temperature parameter displays the temperature conversion of the voltage input signal to the PCM from the transmission fluid temperature (TFT) sensor. When the TFT is high 151°C (304°F), the signal voltage is low, 0 volts. When the TFT is low -40°C (-40°F), the signal voltage is high, 5 volts.

Transmission ISS: The Transmission Input Shaft Speed parameter displays the rotational speed of the transmission input shaft as expressed in revolutions per minute.

Transmission OSS: The Transmission Output Shaft Speed parameter displays the rotational speed of the transmission output shaft as expressed in revolutions per minute.

Vehicle Speed: This parameter is the vehicle speed sensor (VSS) input signal converted by the PCM to be displayed as vehicle speed in both metric and English units.