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2023 XLT Hybrid with ~33k miles, had my check engine light initially come on in the afternoon September 27th. Since Ford dealers were already closed on a Saturday, I got the free scan from Autozone that came back with a P0402. It cleared the next day but then came back on October 3rd. I was able to get Ford to scan and verify the same P0402 code, which prompted them to replace the EGR valve assembly (p/n FMC-LX6Z-9D475-A). The code cleared and I thought this relatively simple fix would take care of it.
Unfortunately, the code came back on Oct 20th, cleared again and re-surfaced Oct 24th, this time staying on through the weekend. Ford diagnosed the same P0402, and again stated EGR valve replacement. I thought this repeat failure indicated the pressure sensor, not the newly installed valve, was bad per other threads on this forum, mainly Customer Satisfaction Program 24N04 - What to replace? and Service Engine Soon: Engine control system has detected that the exhaust gas recirculation system flow was higher than expected for operating cond.. However, pinpoint testing indicated the sensor was not the issue and the new valve was also bad.
Once they started replacement and did visual inspection on the valve, they found evidence of coolant leaking from the adjacent EGR cooler (p/n FMC-LX6Z-9F464-C) and ended up replacing both the valve and the cooler. This may have been the cause of the previous replacement to fail so quickly. There is a Customer Satisfaction Program 24N04 for the exhaust gas heat recovery system but the error codes don't mention 0402 so I'm not sure if it's related or not. No code after pick-up so hopefully this resolved the issue.
Short version, fi you get P0402 don't assume it's the sensor and ask to have the valve inspected for evidence of coolant leakage.
Edit: Check engine light came back this evening, and was able to get it to the dealer right before service closed. They were able to scan the code and confirm P0402 is still there. Reviewing the service documentation, the technician never checked the sensor, but did not think that was the cause. I had the service manager print TSB 23-2059 for the differential pressure EGR sensor and attach it to the code scan documentation. Bringing it back to service on Monday, will see what happens.
Unfortunately, the code came back on Oct 20th, cleared again and re-surfaced Oct 24th, this time staying on through the weekend. Ford diagnosed the same P0402, and again stated EGR valve replacement. I thought this repeat failure indicated the pressure sensor, not the newly installed valve, was bad per other threads on this forum, mainly Customer Satisfaction Program 24N04 - What to replace? and Service Engine Soon: Engine control system has detected that the exhaust gas recirculation system flow was higher than expected for operating cond.. However, pinpoint testing indicated the sensor was not the issue and the new valve was also bad.
Once they started replacement and did visual inspection on the valve, they found evidence of coolant leaking from the adjacent EGR cooler (p/n FMC-LX6Z-9F464-C) and ended up replacing both the valve and the cooler. This may have been the cause of the previous replacement to fail so quickly. There is a Customer Satisfaction Program 24N04 for the exhaust gas heat recovery system but the error codes don't mention 0402 so I'm not sure if it's related or not. No code after pick-up so hopefully this resolved the issue.
Short version, fi you get P0402 don't assume it's the sensor and ask to have the valve inspected for evidence of coolant leakage.
Edit: Check engine light came back this evening, and was able to get it to the dealer right before service closed. They were able to scan the code and confirm P0402 is still there. Reviewing the service documentation, the technician never checked the sensor, but did not think that was the cause. I had the service manager print TSB 23-2059 for the differential pressure EGR sensor and attach it to the code scan documentation. Bringing it back to service on Monday, will see what happens.
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