CX-5 CEL, P0421. PCM programming issue?
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Joined: May 2021
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From: Canada
CX-5 CEL, P0421. PCM programming issue?
I'm trying to help my cousins who recently bought a 2015 CX-5 with mileage over 80K. They got a CEL and took it to a neighborhood mechanic who read a P0421 (Catalytic Converter: Warm Up Catalyst Efficiency Below Threshold (Bank 1)) Other than the light, they have not noticed any issues. The car runs great according to them.
They called the local dealer and gave their VIN, talked to someone in the service department, but I don't think it was a mechanic/technician. The person at the dealer said a catalytic converter wouldn't be covered under warranty after 80K miles. But I do wonder how well they looked into this issue. Because I found this pretty quick when searching online. They aren't 100% sure, but they are pretty sure theirs is a 2.5. A P0421 could be a dead cat, it could be a suspicious oxygen sensor, or sounds like it could be a computer error that's fixable with some new programming? Or a newer PCM at worst? Anyone know anything about these issues on a CX-5??? Anyone replaced a cat, or oxygen sensor or PCM on a 2015 CX-5? Looks like the forward cat on these cars is built in to the exhaust manifold? That sounds like an expensive part and plenty of shop time to put in!
08/04/2015
Mazda Bulletin No: 01-016/15
NHTSA ID: 10105502
Subject: Bulletin No: 01-016/15 CHECK ENGINE LIGHT ON WITH DTC P0421
2014-15 CX-5 (2.5L A/T only)
DESCRIPTION Some vehicles may experience the check engine light on with OTC P0421 :00 (Catalytic converter system) without experiencing poor engine performance or misfire (Mitsubishi PCM only). This is caused by improper control logic of the PCM that may detect false error of the A/F sensor, resulting in false detection of P0421. To correct the problem, the control logic of the PCM has been changed.
SB-10105502-2532.pdf
They called the local dealer and gave their VIN, talked to someone in the service department, but I don't think it was a mechanic/technician. The person at the dealer said a catalytic converter wouldn't be covered under warranty after 80K miles. But I do wonder how well they looked into this issue. Because I found this pretty quick when searching online. They aren't 100% sure, but they are pretty sure theirs is a 2.5. A P0421 could be a dead cat, it could be a suspicious oxygen sensor, or sounds like it could be a computer error that's fixable with some new programming? Or a newer PCM at worst? Anyone know anything about these issues on a CX-5??? Anyone replaced a cat, or oxygen sensor or PCM on a 2015 CX-5? Looks like the forward cat on these cars is built in to the exhaust manifold? That sounds like an expensive part and plenty of shop time to put in!
08/04/2015
Mazda Bulletin No: 01-016/15
NHTSA ID: 10105502
Subject: Bulletin No: 01-016/15 CHECK ENGINE LIGHT ON WITH DTC P0421
2014-15 CX-5 (2.5L A/T only)
DESCRIPTION Some vehicles may experience the check engine light on with OTC P0421 :00 (Catalytic converter system) without experiencing poor engine performance or misfire (Mitsubishi PCM only). This is caused by improper control logic of the PCM that may detect false error of the A/F sensor, resulting in false detection of P0421. To correct the problem, the control logic of the PCM has been changed.
SB-10105502-2532.pdf
Senior Member
Joined: Jun 2017
Posts: 342
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From: Superstition Mountains
Potential reasons for the code:
• Leakage exhaust system
• A/F sensor looseness
• HO2S looseness
• WU-TWC deterioration or malfunction ( Catalytic convertor )
• PCM malfunction
All are possible in a 6 year old vehicle. The dealer can determine the actual engine with the VIN.
• Leakage exhaust system
• A/F sensor looseness
• HO2S looseness
• WU-TWC deterioration or malfunction ( Catalytic convertor )
• PCM malfunction
All are possible in a 6 year old vehicle. The dealer can determine the actual engine with the VIN.
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