DTC Advanced Diagnostics: P1890
DTC P1890 : CVT Speed Control System
General Description
The shift control system controls each gear position using a map stored in the transmission control module (TCM) memory. The shift control system controls the CVT drive pulley pressure control solenoid valve and the CVT driven pulley pressure control solenoid valve based on vehicle speed and the throttle position to keep the drive pulley speed close to the target rpm. It does this by varying the hydraulic pressure applied to the drive and driven pulleys and providing feedback on the difference between the target drive pulley speed and the actual drive pulley speed when driving. It supplies high hydraulic pressure to the driven pulley and enlarges the driven pulley belt diameter when shifting to a lower ratio. It supplies high hydraulic pressure to the drive pulley and enlarges the drive pulley belt diameter when shifting to a higher ratio. If the difference between the target drive pulley speed and the actual drive pulley speed falls within a certain range when in D, S, or R position/mode, the TCM detects a malfunction in the CVT shift function and stores a DTC.
Monitor Execution, Sequence, Duration, DTC Type
| Execution | Continuous |
| Sequence | None |
| Duration | 18 seconds or more |
| DTC Type | One drive cycle, MIL off, Shift position indicator blinks |
Enable Conditions
| Condition | Minimum | Maximum | |
|---|---|---|---|
| Drive pulley speed [Input Shaft (Drive Pulley) Speed rpm] | 576 rpm | - | |
| Vehicle speed [Vehicle Speed] | 9 mph (14 km/h) | - | |
| Accelerator pedal position | 4.7 deg. | - | |
| Shift position/mode | D, S, R | ||
[ ]: HDS Parameter
Malfunction Threshold
The difference between the target drive pulley speed and the actual drive pulley speed [Input Shaft (Drive Pulley) Speed rpm] is 500 rpm or more for at least 18 seconds.
Possible Cause
The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
- CVT shift function failure
Confirmation Procedure
Operating Condition
- Start the engine.
- Accelerate gradually to 37 mph (60 km/h) and drive at least 1 minute at 37 mph (60 km/h).
- Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.
Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected, the shift position indicator blinks and a Pending DTC, a Confirmed DTC, and the freeze data are stored in the TCM memory. The MIL does not come on.
Conditions for clearing the DTC
The shift position indicator comes off by turning the vehicle to the OFF (LOCK) mode. The Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool clear command.