P0722

DIAGNOSTIC TROUBLE CODE (DTC) P0722 AUTOMATIC TRANSMISSION VEHICLE SPEED SENSOR (A/T VSS) LOW INPUT





Circuit Description
Vehicle speed is provided to the Powertrain Control Module (PCM) by the Automatic Transmission Vehicle (Shaft) Speed Sensor (A/T VSS), which is a Permanent Magnet (PM) generator mounted to the transmission case. The PM generator produces an AC voltage as the speed sensor rotor teeth pass in front of the sensor's magnetic field. The AC voltage level increases as the speed of the vehicle increases. The PCM then converts the AC voltage into a digital signal. The PCM uses the vehicle speed to determine shift timing, TCC apply, TCC release, and gear ratio calculations.
When the PCM detects a low vehicle output speed when the vehicle has a large engine speed in a drive gear, then DTC P0722 sets.


Conditions For Setting DTC
- Transmission not in P (Park) or N (Neutral).
- No MAP DTCs.
- No A/T ISS DTC(s) P0716 or P0717.
- No TP DTCs.
- No TFP Val. Position Sw. DTC P1810.
- TP is greater than 12%.
- MAP is greater than 10 kPa.
- Transmission input speed is greater than 1000 rpm.
- Engine speed is greater than 1500 rpm.
- Output speed is less than 2 mph (3.2 km/h).
- All the above conditions are met for five seconds.


Action Taken When The DTC Sets
- PCM will illuminate the Malfunction Indicator Lamp (MIL) after two consecutive trips with a failure reported.
- PCM freezes shift adapts from being updated.
- PCM commands maximum line pressure.
- PCM calculates output speed based on input speed, engine speed, and commanded gear.
- DTC P0722 will be stored in PCM memory.


Conditions For Clearing The DTC
- The PCM will turn the MIL off after the transmission output speed is greater than 500 rpm for three seconds and three consecutive ignition cycles.
- History DTC(s) can be cleared by using a Scan Tool.


Diagnostic Aids
- Condition may be intermittent. Check for loose output speed sensor mounting or poor sensor connection.
- Inspect for a damaged output speed sensor or transmission rotor teeth.
- Inspect the wiring for poor electrical connections at the PCM and at the A/T VSS. Look for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension-as well. Also check for chafed wires that could short to bare metal or other wiring. Inspect for broken wire inside the insulation.
- If diagnosing for a possible intermittent short or open condition, move or massage the wiring harness while observing test equipment for a change.


Test Description
The numbers below refer to the numbered steps on the diagnostic chart.
3. This test checks the ANT VSS for correct resistance.
4. This tests the A/T VSS ability to produce an AC current and the integrity of the wiring to the PCM.






DIAGNOSTIC TROUBLE CODE (DTC) P0722 AUTOMATIC TRANSMISSION VEHICLE SPEED SENSOR (A/T VSS) LOW INPUT