The Honda P1891 DTC is related to the start clutch, which is responsible for the clutch piston hydraulic pressure that helps to put engine power to the ground. If this system is not able to function properly, your Honda CVT transmission will not be able to propel the car down the road.
How Serious is the Code?
Mostly used for Honda CVT transmissions, the P1891 diagnostic trouble code generally gets stored if there is a major malfunction in the transmission’s hydraulic control system. Hydraulic pressure is what moves the drive pulleys around and allows the CVT drive belt to change the gear ratio. Should there be an issue with one of these transmission parts, the Honda CVT won’t be able to transmit engine power to the drive wheels.
Symptoms of a P1891 include:
- Transmission suddenly changes to a low gear ratio at cruising speed, which causes a spike in engine RPM
- Poor engine performance
- Check engine light
- Damaged or corroded wiring/connectors
- Failed TCM
- Failed clutch pressure control valve
- Start clutch out of adjustment
- Failed shift inhibitor valve
- Failed CVT start clutch pressure control solenoid
How to Diagnose the Code?
In order to diagnose a P1891 OBDII diagnostic trouble code, it’s best to start by inspecting the wiring and connectors on the transmission wiring harness. If no issues are found, then a driving test will need to be performed while monitoring data from the CVT speed sensor and driven pulley speed sensor. This procedure should help to narrow down the offending part.
What Repairs Will Fix P1891?
- Repair or replace damaged wiring/connectors
- Replace TCM
- Replace clutch pressure control valve
- Replace shift inhibitor valve
- Replace CVT start clutch pressure control solenoid adjust start clutch
- Install remanufactured CVT transmission