DTC Advanced Diagnostics: P0718
DTC P0718:Input Shaft (Mainshaft) Speed Sensor (Intermittent Failure)

General Description


The input shaft (mainshaft) speed sensor is attached to the outside of the transmission housing. The input shaft (mainshaft) speed sensor generates a pulsing signal according to the speed of the idler gear on the input shaft (mainshaft). Using that signal, the powertrain control module (PCM) determines the speed of the input shaft (mainshaft). If no pulses occur with the input shaft (mainshaft) rotating, the PCM detects a malfunction that may be caused by an open, a temporary open, or a short to ground. Based on the fluctuation of the vehicle speed measured by 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
500 milliseconds
DTC Type
Two drive cycles, MIL on, A/T gear position indicator blinks
OBD Status
PASSED/FAILED/NOT COMPLETED (STILL TESTING)

Enable Conditions
Condition
Minimum
Maximum
Vehicle speed
[VEHICLE SPEED]
13 mph (20 km/h)
–
Battery voltage
[BATTERY VOLTAGE]
11 V
–
No active DTCs set (prevents monitor from running)
P0716, P0717, P0721, P0722
Other
Not during shifting
Not when an output shaft (countershaft) speed sensor intermittent failure is detected
[ ]: HDS Parameter

Malfunction Threshold
The fluctuation of the vehicle speed measured by the input shaft (mainshaft) speed sensor in 10 milliseconds is 4 mph (6 km/h) or more, and it fluctuates at least six times within 500 milliseconds.

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.
Input shaft (mainshaft) speed sensor line intermittent short to ground
Input shaft (mainshaft) speed sensor line intermittent open (includes connector loose connection or disconnection)
Input shaft (mainshaft) speed sensor intermittent 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 so it shifts from 1st to 6th gear.
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 during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on, the A/T gear position indicator blinks, and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC
The A/T gear position indicator comes off by pressing the engine start/stop button to select the OFF mode. 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.