Circuit Description

PCM directly controls the ground for the linear EGR valve when certain conditions have been met. PCM contains a diode feedback circuit which dissipates energy when the valve is cycled off. When PCM grounds the valve, a diagnostic feedback signal can determine is valve had actually moved. This DTC has been defined to monitor the feedback signal. This diagnostic will determine if the position feedback signal properly falls within the correct range under different valve operating conditions.

DTC will set when the actual closed value does not match the learned closed value within 20 seconds if RPM is less than 5000 and the actual versus learned value is greater than 0.2 volt, or RPM is greater than 5000 and the actual versus learned value is greater than 0.4 volt.

When PCM recognizes that the parameters for setting DTC P1404 have been set, the diagnostic software waits until the EGR cycles open 25 percent or greater, 3 times and then retest. If after 3 cycles, the actual versus learned values is not within the parameters, DTC will be stored and MIL will illuminate.

When this DTC sets, some EGR functions will be disabled for the duration of that ignition cycle. When repairs are complete, DTCs must be cleared to allow proper operation.