DTC Advanced Diagnostics: P1840
DTC P1840:CVT Speed Sensor Circuit Forward Rotation Range/Performance

General Description


Tr1
Tr2
Pulse signal voltage level
OFF
OFF
VOH
OFF
ON
VOM
ON
OFF
VOL

The CVT speed sensor is attached to the outside of the torque converter housing. The CVT speed sensor consists of a semiconductor to detect the position of the secondary driven gear. When the secondary driven gear rotates, the magnetic flux in the CVT speed sensor changes. The changes of magnetic flux are converted into pulsing signals to the powertrain control module (PCM). The rotational direction of the secondary driven gear is detected by the voltage level of the pulsing signals. If the driving condition and the detected voltage level of the pulsing signals do not match, the PCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status
Execution
Continuous
Sequence
None
Duration
2 seconds or more
DTC Type
Two drive cycles, MIL off, A/T gear position indicator blinks
OBD Status
PASSED/FAILED/NOT COMPLETED (STILL TESTING)

Enable Conditions
Condition
Minimum
Maximum
Elapsed time after forward clutch engage completion
3 seconds
–
Engine speed
[ENGINE SPEED]
500 rpm
–
Drive pulley speed [Input Shaft (Drive Pulley) Speed rpm]
500 rpm
–
Forward clutch commanded pressure
295 kPa (3.0 kgf/cm2, 42.7 psi)
–
Vehicle speed
[VEHICLE SPEED]
19 mph (30 km/h)
–
Shift lever position
5-position continuously variable transmission
D, S
6-position continuously variable transmission
D, S, L
Drive pulley rotational direction
Forward direction
No active DTCs set (prevents monitor from running)
P0501, P0502, P0705, P0706, P0716, P0717, P0792, P0793, P0962, P0963, P0966, P0967, P0970, P0971, P0976, P0977, P1717, P1841, P1844, P1845, P2720, P2721
Other
Not when the shift lever is being shifted
[ ]: HDS Parameter

Malfunction Threshold
The CVT speed sensor outputs [Direction of Secondary-shaft Rotation] a reverse direction signal for at least 2 seconds when driving in forward position.

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.
CVT speed sensor failure
PCM internal circuit failure

Confirmation Procedure
Operating Condition

1.
Start the engine.
2.
Drive the vehicle in D at a speed of 19 mph (30 km/h) or more for at least 5 seconds.
3.
Slow down and stop the vehicle.
4.
Turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.
5.
Repeat Driving Pattern steps 1 through 3.
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 A/T gear position indicator blinks and a Confirmed DTC and the freeze data are stored. The MIL does not come on.

Conditions for clearing the DTC
The A/T gear position indicator comes off by turning the ignition switch to LOCK (0), or pressing the engine start/stop button to select the OFF mode. The Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command.