Mazda 3 - Dtc P0420 [Z6]

Mazda 3 Workshop Manual – Engine + Wiring Diagrams + Diagnostic Trouble Codes
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• Are any DTCs present?
DTC P0420 [Z6]
B3E010200400W02
DTC P0420
Catalyst system efficiency below threshold
DETECTION
CONDITION
• The PCM compares the number of the front HO2S and rear HO2S inversions for a
predetermined time. The PCM monitors the number of inversions the rear side performs
while the front side inverts for a specified number of times when the following
monitoring conditions are met. The PCM detects the inversion ratio. If inversion ratio is
below the threshold, the PCM determines that the catalyst system has deteriorated.
MONITORING CONDITION
- HO2S, HO2S heater and TWC repair verification drive mode
- Engine speed is 1,500- 3,000 rpm.
- Calculated TWC temperature in PCM is more than 600 °C
{1112 °F} (MTX), more than 620 °C {1148 °F} (ATX).
- Calculated load is 17- 48 %.*
1
*
1
: Maximum calculated load value varies depending on engine speed.
Diagnostic support note
• This is a intermittent monitor (Catalyst).
• The MIL illuminates if the PCM detects the above malfunction condition in two
consecutive drive cycles or in one drive cycle while the DTC for the same malfunction
has been stored in the PCM.
• DIAGNOSTIC MONITORING TEST RESULTS and PENDING CODE are available if
the PCM detects the above malfunction condition during the first drive cycle.
• FREEZE FRAME DATA is available.
• The DTC is stored in the PCM memory.
POSSIBLE
CAUSE
• TWC deterioration or malfunction
• Exhaust gas leakage
• Loose front HO2S
• Loose rear HO2S
• Front HO2S malfunction
Diagnostic procedure
STEP
INSPECTION
ACTION
1
Yes
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