EVAP System Leak Inspection Using M-MDS

NOTE: EVAP system test outline

The EVAP system test, which can substituted for the run drive cycle as an EVAP control system repair confirmation method, can be done while operating the M-MDS in the KOEO (Key On Engine Off) condition instead of actually driving the vehicle.

EVAP system test description

The EVAP system test finds gas leaks in the system using the PCM to monitor changes in the air pump load current of the EVAP system leak detection pump. This test starts after sending an on-demand test signal from the M-MDS to the PCM. The PCM controls the air pump and change-over-valve operation and also stores the load current of the air pump as follows:
1. The PCM commands turn the air pump on and retrieve the air pump load current value (LDP_MON PID) as a reference current (LDP_REF PID).
2. After retrieving a reference current value, the PCM commands the change-over-valve to open, then captures the air pump load current value (LDP_MON PID) as idle current (LDP_IDL PID). The EVAP system will be pressurized from this phase.
3. The PCM continues to monitor the air pump load current value (LDP_MON PID) until the end of the test.
You can confirm whether any evaporative gas leak occurred or not by reading the test results.

Fig 1: EVAP Control System Run Drive Cycle
Courtesy of MAZDA MOTORS CORP.

EVAP system malfunction judgment

The PCM calculates the stored air pump load current value and send the results to the M-MDS as DTCs:

Fig 2: EVAP Control System Operation Diagram
Courtesy of MAZDA MOTORS CORP.

DTC No.	Condition
P0442	Evaporative emission control system leak detected (small leak)
P0446	Change over valve (COV) (EVP system leak detection pump) stuck close
P0455	Evaporative emission control system leak detected (gross leak)
P0456	Evaporative emission system leak detected (very small leak)
P2401	EVAP system leak detection pump motor circuit low
P2402	EVAP system leak detection pump motor circuit high
P2404	EVAP system leak detection pump sense circuit problem
P2405	EVAP system leak detection pump sense circuit low input
P2407	EVAP system leak detection pump sense circuit intermittent