Circuit Description
The automatic transmission output speed sensor is a variable reluctance magnetic pickup sensor and is located in the inside rear of the transmission case, above the control valve body and accumulator assembly. It is mounted in the case opposite the rear internal gear. The rear internal gear is splined to the transmission output shaft assembly.
The sensor consists of a permanent magnet surrounded by a coil of wire. As the output shaft and rear internal gear rotate, an alternating current (AC) is induced into the coil by the 'teeth' on the rear internal gear as they pass by the magnetic pickup.
The output of this speed sensor produces an AC voltage signal proportional to the rotational speed of the rear internal gear, which is rotating at vehicle speed.
Within the TCM, the AC voltage is converted to a 5 volt square wave form and this wave form is interpreted as the transmission output speed.
The TCM uses transmission input and output speeds to help determine line pressure, transmission shift patterns, TCC apply pressure, gear ratios and TCC slippage for diagnostic purposes.
If the TCM detects no vehicle speed when there is engine speed in a drive gear range, then DTC P0723 sets, which is a type 'B' DTC.
Conditions for Running the DTC
| • | Ignition voltage is between 8.0 and 18.0 volts. |
| • | Engine speed is between 450 to 6,800 RPM for at least 5 seconds. |
| • | The following DTCs are not set: |
| - | P0716 or P0717 - Transmission Input Speed Sensor |
| - | P1843 - 1-2 Shift Solenoid Electrical Fault (Short to Voltage) |
| - | No engine torque DTCs. |
| - | No throttle system DTCs. |
| • | The transmission input speed has not increased more than 500 RPM for at least 2 seconds. |
| • | The transmission output speed is greater than 1,400 RPM for 2 seconds or greater. |
| • | The transmission output speed has not changed greater than 500 RPM for at least 2 seconds. |
| OR |
| • | The transmission output speed has not decreased for at least 2 seconds. |
Conditions for Setting the DTC
The transmission output speed drops greater than 1,300 RPM for at least 3 seconds.
Action Taken When the DTC Sets
| • | The TCM requests the Powertrain Interface Module (PIM) to illuminate the Check Powertrain Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the 'Conditions for Setting the DTC' have been met. |
| • | At the time of the first failure, the TCM records the operating conditions when the 'Conditions for Setting the DTC' are met. The TCM stores this information as a Failure Record. |
| • | At the time of the second failure, the ECM records the operating conditions when the 'Conditions for Setting the DTC' have been met. The ECM stores this information as a Freeze Frame. |
| • | TCM will determine the vehicle speed from the automatic transmission input speed sensor signal as well as the commanded gear ratio (signals to the TCM from the three shift solenoids). |
| • | The TCM also turns off the pressure control solenoid (causing maximum line pressure). |
| • | The TCM freezes the transmission adaptive learning function. |
| • | The TCM stores DTC P0722 into TCM history. |
Conditions for Clearing the MIL/DTC
| • | The PIM turns off the Check Powertrain MIL after the sixth consecutive drive trip in which the TCM does not send a Check Powertrain MIL illumination request. |
| • | Tech 2 can clear the DTC. |
| • | The TCM clears the DTC from its memory (history DTC) if the vehicle completes 40 warm-up cycles without a non-emission related DTC occurring. |
| • | The TCM cancels the default actions when the ignition is off long enough to power down the TCM. |
Diagnostic Aids
Ensure that the transmission input speed sensor to transmission case bolt is correctly tightened.
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
3. Checks to determine if there is a short to voltage on the input speed sensor signal circuit.
4. Checks to determine if there is a short to ground on the input speed sensor signal circuit.
6. Verifies the circuit continuity from the TCM connector to, through, and from the output speed sensor.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Automatic Transmission Controls Schematics For information on testing wiring faults, refer to Wiring Systems. | ||||
1 | Has the Diagnostic System Check - Automatic Transmission been completed? | -- | Go to Step 2 | |
2 |
Does the Tech 2 display output speed sensor above the specified value? | More than 100 rpm | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 |
3 |
Is voltage reading less than the specified value? | Less than 0.3 volts | Go to Step 4 | Go to Step 5 |
4 |
Is resistance greater than the specified value? | More than 500 kΩ | Go to Step 6 | Go to Step 9 |
5 |
Does either check indicate a short to voltage in the transmission wiring? | -- | Repair short to voltage in relevant circuit. Go to Step 13 | Go to Step 11 |
6 | Using a digital ohmmeter, measure the resistance between transmission wiring harness TCM connector A112-T68, terminals X1-1 and X1-2. Is resistance within specified values? | 325-485 Ω @ 20°C 385-575 Ω @ 70°C | Go to Step 10 | If less than specified, go to Step 7. If greater than specified, go to Step 8. |
7 |
Does either check indicate an internal short circuit in the transmission wiring? | -- | Repair internal short circuit in relevant circuit. Go to Step 13 | Go to Step 11 |
8 |
Does either check indicate an open circuit in the transmission wiring? | -- | Repair open in relevant circuit. Go to Step 13 | Go to Step 11 |
9 |
Does either check indicate a short to ground in the transmission wiring? | -- | Repair short to ground in relevant circuit. Go to Step 13 | Go to Step 11 |
10 |
Is the transmission internal wiring harness OK? | -- | Go to Step 11 | Replace the transmission internal wiring harness. Refer to Transmission Internal Electrical Harness Replacement Go to Step 13 |
11 |
Was any damage to components found? | -- | For sensor damage, replace the damaged component. If rear internal gear damage is found, replace the transmission. Refer to Transmission Replacement | Go to Step 12 |
12 | Replace the TCM.Refer to Transmission Control Module Replacement for replacement procedures. Is the replacement complete? | -- | Go to Step 13 | -- |
13 | Perform the following procedure to verify the repair:
Verify that Tech 2 indicates an output speed sensor signal of greater than 500 RPM for more than 2 seconds. Has the test run and passed? | -- | System OK | Go to Step 2 |
When all diagnosis and repairs are completed, clear all DTCs and verify correct operation. | ||||
