GM Service Manual Online
For 1990-2009 cars only
1-2 Sol (Solenoid) 2-3 Sol (Solenoid): Scan tool displays ON or OFF. These parameters are the commanded states of the 1-2 and the 2-3 shift solenoid valves. ON indicates a commanded energized solenoid state, and OFF indicates a commanded nonenergized solenoid state.

1-2 Sol (Solenoid) Open: Scan tool displays YES or NO. This parameter indicates whether an open or a short to ground exists in the 1-2 shift solenoid valve feedback signal to the PCM. The 1-2 shift solenoid valve must be commanded OFF for this parameter to work.

1-2 Sol (Solenoid) Shorted: Scan tool displays YES or NO. This parameter indicates whether a short to battery (B+) exists in the 1-2 shift solenoid valve feedback signal to the PCM. The 1-2 shift solenoid valve must be commanded ON for this parameter to work.

2-3 Sol (Solenoid) Open: Scan tool displays YES or NO. This parameter indicates whether an open or a short to ground exists in the 2-3 shift solenoid valve feedback signal to the PCM. The 2-3 shift solenoid valve must be commanded OFF for this parameter to work.

2-3 Sol (Solenoid) Shorted: Scan tool displays YES or NO. This parameter indicates whether a short to battery (B+) exists in the 2-3 shift solenoid valve feedback signal to the PCM. The 2-3 shift solenoid valve must be commanded ON for this parameter to work.

2nd Gear Start Switch: Scan tool displays ON or OFF. This parameter indicates that a 2nd gear start has been requested. When ON displays, the 2nd gear start switch will turn on the 2-3 shift solenoid valve and turn off the 1-2 shift solenoid valve. The vehicle will then start off in 2nd gear for better traction. The following gears will shift as normal. When OFF displays, a normal shift control program is effective and the vehicle will start off in 1st gear. Wide Open Throttle (WOT) will override the 2nd gear start switch and the vehicle will start off in 1st gear.

A/C Clutch: Scan tool displays ON or OFF. This represents the PCM commanded state of the A/C compressor clutch relay driver circuit. The A/C compressor clutch should be engaged when ON displays. When the display indicates ON, the line pressure and the shift times will be adjusted for the additional engine load.

Cruise Enable: Scan tool displays ON or OFF. When the display indicates ON, the PCM is allowing cruise control operation. When the display indicates OFF, the PCM has disabled cruise control operation. The PCM has the ability to disable cruise control under certain conditions. When the cruise control is ON, shift patterns will be altered for 2-3 and 3-4 upshifts for 4-3 and 3-2 downshifts.

Current Gear: Scan tool displays 1, 2, 3, or 4. The PCM looks at the transmission range position and the gear commanded by the PCM. The actual forward gear that the transmission is in will be the lower of the two because the manual valve overrides the PCM commanded gear.

ECT (Engine Coolant Temperature): Scan tool range -40°C to 151°C (-40°F to 304°F). The 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 which 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 Run Time: Scan tool displays SECONDS. This parameter indicates the time elapsed since the engine was started. If the engine is stopped, this parameter is reset to 00:00:00.

Engine Speed (RPM): Scan tool range 0-9999 RPM. The engine speed is computed by the PCM from the fuel control reference input (the crankshaft position sensor). This parameter indicates the rotational speed of the engine expressed as revolutions per minute.

Gear Ratio: Scan tool range 0.00-3.98. This display is the actual transmission gear ratio as the transmission operates through all Drive, Reverse and Park/Neutral ranges.

Hot Mode: Scan tool displays YES or NO. This display indicates the Automatic Transmission Fluid Temperature (TFT). NO indicates that the TFT has not exceeded 130°C (266°F). YES indicates that the TFT has exceeded 130°C (266°F) and has not cooled to 120°C (248°F) for more that 5 seconds. Note: these numbers are approximate. They differ with transmissions.

MAF (Mass Air Flow): Scan tool range 0.0-512 g/s. The MAF sensor input signal to the PCM is a frequency which varies from around 3000 Hz at idle to above 7000 Hz at Wide Open Throttle (WOT). The PCM converts this frequency to grams of air per second, which indicates the amount of air entering the engine.

MAP (Manifold Absolute Pressure): Scan tool range 10-105 kPa, 0.00-4.97 volts. The MAP sensor measures the change in the intake manifold pressure from the engine load, the EGR flow, and the speed changes. As intake manifold pressure increases, the intake vacuum decreases, resulting in a higher MAP sensor voltage and kPa reading. The MAP sensor signal is used to monitor intake manifold pressure changes during the EGR flow test, to update the BARO reading, and as an enabling factor for several of the diagnostics.

Speed Ratio: Scan tool range 0-255. This parameter indicates engine speed divided by vehicle speed.

TCC (Torque Converter Clutch) Brake Switch: Scan tool range Open/Closed. When the brake pedal is applied, the TCC brake switch sends a signal to the PCM to disengage the TCC and disable cruise control.

TCC PWM (Torque Converter Clutch Pulse Width Modulation) Solenoid: Scan tool range 0% to 100%. This display indicates the commanded percent of the TCC PWM sol valve ON time. 90% represents an energized commanded state and 0% represents a de-energized commanded state. the commanded state is applied at vehicle speeds that are above approximately 16 km/h (10 mph).

TCC PWM (Torque Converter Clutch Pulse Width Modulation) Open: Scan tool displays YES or NO. This parameter indicates whether an open or a short to ground exists in the TCC PWM sol valve feedback signal to the PCM. The TCC PWM sol valve must be commanded OFF for this parameter to work. The Scan tool will display YES only while the TCC PWM sol valve is OFF. The display will pulsate.

TCC PWM (Torque Converter Clutch Pulse Width Modulation) Shorted: Scan tool displays YES or NO. This parameter indicates whether a short to battery (B+) exists in the TCC PWM sol valve feedback signal to the PCM. The TCC PWM sol valve must be commanded ON for this parameter to work. The Scan tool will display YES only while the TCC PWM sol valve is ON. The display will pulsate.

TCC (Torque Converter Clutch) Enable: Scan tool displays ON or OFF. This display indicates the commanded state of the TCC sol valve. ON indicates an energized solenoid and OFF indicates a non-energized solenoid. The commanded states of ON and OFF occur under various vehicle speeds and various PCM inputs.

TCC (Torque Converter Clutch) Enable Open: Scan tool displays YES or NO. This parameter indicates whether an open or a short to ground exists in the TCC sol valve feedback signal to the PCM. The TCC sol valve must be commanded OFF for this parameter to work.

TCC (Torque Converter Clutch) Enable Shorted: Scan tool displays YES or NO. This parameter indicates whether a short to battery (B+) exists in the TCC sol valve feedback signal to the PCM. The TCC sol valve must be commanded ON for this parameter to work.

TCC (Torque Converter Clutch) Slip Speed: Scan tool range -4080 to +4079 RPM. This display is the difference between the transmission output shaft RPM and the engine RPM. A negative value indicates deceleration: the engine RPM is less than the output shaft RPM. A positive value indicates acceleration: the engine RPM is more than the output shaft RPM. A value of zero indicates that TCC is applied: the engine RPM is equal to the output shaft RPM.

TFT (Automatic Transmission Fluid Temperature):  Scan tool range -40°C to 140°C (-40°F to 284°F). This display is the temperature conversion of the voltage input signal to the PCM of the TFT. When the TFT is high (140°C, 284°F), the signal voltage is low (0.00 volts). When the TFT is low (-40°C, -40°F), the signal voltage is high (5.00 volts).

TFT (Automatic Transmission Fluid Temperature) Sensor: Scan tool range 0.00-5.00 volts. This display shows the voltage drop across the TFT sensor. The PCM applies 5 volts to the TFT sensor circuit. The sensor is a thermistor which changes internal resistance as the 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 transmission. As the sensor warms (the internal resistance decreases), the voltage signal will decrease. The PCM interprets the lower voltage as a warm transmission.

TP (Throttle Position) Sensor: Scan tool range 0.00-5.00 volts. This parameter indicates the voltage being monitored by the PCM on the TP sensor signal circuit.

TP (Throttle Position) Angle: Scan tool range 0%-100%. The TP Angle 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 (Transmission) OSS (Output Speed Sensor): Scan tool range 0-8191 RPM. This display indicates the rotational speed of the transmission output shaft as expressed in revolutions per minute.

Vehicle Speed (km/h, mph): Scan tool range 0-255 km/h (0-158 mph). This parameter is the Vehicle Speed Sensor (VSS) input signal converted by the PCM to be displayed in both metric and English units.