DTC P0721
DTC P0721: Output Shaft (Countershaft) Speed Sensor (Range/Performance)
General Description
The output shaft (countershaft) speed sensor is attached to the outside of the transmission housing. The output shaft (countershaft) speed sensor generates a pulsing signal according to the speed of the park gear on the output shaft (countershaft). Using that signal, the powertrain control module (PCM) determines the speed of the output shaft (countershaft). If no pulses occur with the output shaft (countershaft) rotating, the PCM detects a malfunction that may be caused by an open, a temporary open, or a short to ground. Based on the velocity ratio measured by the output shaft (countershaft) speed sensor and the input shaft (mainshaft) speed sensor, the PCM detects a malfunction and stores a DTC.
Monitor Execution, Sequence, Duration, DTC Type, OBD Status
| Execution | Continuous |
| Sequence | None |
| Duration | 10 seconds or more |
| DTC Type | One drive cycle, MIL on, A/T gear position indicator blinks |
| OBD Status | PASSED/FAILED/NOT COMPLETED (STILL TESTING) |
Enable Conditions
| Condition | Minimum | Maximum |
|---|---|---|
| Engine speed [ENGINE SPEED] |
500 RPM | - |
| Vehicle speed [VEHICLE SPEED] |
13 mph (20 km/h) | - |
| Battery voltage [BATTERY VOLTAGE] |
11 V | - |
| Shift lever position | D | |
| No active DTCs set (prevents monitor from running) | P0705, P0706, P0716, P0717, P0722, P0962, P0963, P0966, P0967, P0970, P0971, P0973, P0974, P0976, P0977, P0979, P0980, P2720, P2721 | |
| Other | Not during shifting | |
| Not when the shift lever is being shifted | ||
| No electrical noise in the input shaft (mainshaft) speed sensor output circuit | ||
| Except 1st gear | ||
[ ]: HDS Parameter
Malfunction Threshold
The vehicle speed measured by the input shaft (mainshaft) speed sensor [INPUT SHAFT (MAINSHAFT) SPEED] divided by the vehicle speed measured by the output shaft (countershaft) speed sensor [OUTPUT SHAFT (COUNTERSHAFT) SPEED] is greater than 7.0 for at least 10 seconds.
Possible Cause
NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
- Output shaft (countershaft) speed sensor line short to ground
- Output shaft (countershaft) speed sensor line open (includes connector loose connection or disconnection)
- Output shaft (countershaft) speed sensor failure
- PCM internal circuit failure
Confirmation Procedure
Operating Condition
- 1.
Start the engine.
- 2.
Drive the vehicle at a speed of 13 mph (20 km/h) or more for at least 10 seconds.
- Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.
With the HDS
None.
Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected, the MIL comes on and a Pending DTC, a Confirmed DTC, and the freeze data are stored in the PCM memory.
Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the battery.