Error Code P1451 is defined as EVAP Control System Canister Vent Solenoid Circuit Malfunction. This code means there’s a leak detected in the EVAP (evaporative emission) system.
This error code is a manufacturer-specific trouble code, as it does not apply to all cars makes. Rather, it applies only to specific 1998 Land Rover Discovery Series I makes, such as Ford. Specification on the definition, troubleshooting, and repairs still vary from one make and model to another.
The EVAP system works by monitoring the canister vent (CV) solenoid circuit for electrical failures. The test fails when the signal moves outside the minimum or maximum specified calibrated parameters for a particular canister vent duty cycle by PCM (powertrain control module, also known as ECM or engine control module in other 1998 Land Rover Discovery Series I makes) command.
As with other error codes, this code activates the Check Engine light and registers the code to the system. In most cases, this error will not cause any drivability issues.
Error Code P1451 means that one or more of the following has happened:
Start your diagnosis for this error code by checking the canister vent solenoid. To check its functioning, monitor the EVAP canister vent solenoid signal PID EVAPCV and the signal voltage (PCM control side). With the valve open, EVAPCV indicates 0% duty cycle and a voltage approximately equal to battery voltage. When the valve is commanded fully closed, EVAPCV shows a 100% duty cycle, and a minimum voltage drop of 4 volts is typical. Output test mode may be used to switch output on/off to verify function.
The easiest fix for this problem is to replace the canister vent solenoid.
This error code is moderately easy to repair, and most often than not, the problem is fixed by just replacing the canister vent solenoid.