This is my follow-up article from May 7 on the 2014 Acura MDX EVAP problem.
If you did not read the article from last month, we were working on a check engine light problem in the evaporative fuel system (EVAP). After testing the car, we found a piece of plastic stuck in the fuel tank pressure sensor vacuum passage. Once we removed the piece of plastic, we ran an EVAP system check again and it passed, but we needed the car to run the EVAP test by itself (not with the scanner). Since the car’s fuel tank was full, we let the customer pick up the car and drive it.
The customer drove the car for about a week. Once the fuel level was at three-quarters, the check engine light came on again. We connected the scanner and pulled codes – the P1454 FTP (fuel tank pressure sensor) circuit range/performance problem that was stored in temporary and permanent memory and code P2422 evaporative emissions (EVAP) canister vent solenoid (CVS) stuck in permanent memory. These two codes were in the system at the last visit, but the one code that did not come back was P0452 FTP sensor circuit low voltage.
Both the fuel tank pressure sensor and the canister vent solenoid are installed in the evaporative charcoal canister. The evaporative emissions charcoal canister’s job is to trap any unwanted fuel vapors from escaping out of the EVAP system. Next, we ran a complete EVAP system test using the scanner. The system passed the test. We then ran specific tests on the fuel tank pressure sensor (P1454) and on the canister vent solenoid (CVS/P2422). Both sensors passed their activation test. The problem is that even though these sensors passed their test, it was unclear if they were correctly operating in and on the evaporative charcoal canister. The other big question was, where did that piece of plastic come from that blocked the EVAP canister filters’ vacuum line? It was becoming increasingly obvious that we had to replace the evaporative charcoal canister.
Since the evaporative charcoal canister traps a large amount of fuel vapor over time, it becomes extremely corrosive inside the canister. This corrosion can cause the canister to deteriorate. The charcoal inside of the canister can become oversaturated and start to fall apart. In the past, we have found EVAP purge valves clogged with pieces of charcoal. Most charcoal canisters come equipped with sensors, but not on the MDX. We had to replace the charcoal canister, the fuel tank pressure sensor and the canister vent solenoid.
Once we had the old canister off the car, we checked to see if we could find any loose pieces of plastic or charcoal. With the sensors removed from the canister, we did find a few small pieces of loose debris in the canister and sensors.
After replacing the charcoal canister, fuel tank pressure sensor and the canister vent solenoid, we cleared codes and started to run monitors. As stated in the first article, it can take days or weeks before the EVAP monitor successfully runs on the car itself. It took us about three days to satisfy the EVAP monitor. Once the EVAP monitor was finally completed, we ran one more EVAP test just to look at the EVAP data. All the data looked great.
Anytime we have to work on EVAP systems, I try my best to explain to customers how difficult it can be to solve. This particular problem was difficult because the charcoal canister was shedding debris into multiple EVAP systems and sensors. The most important thing to remember when working with EVAP is to make sure to follow the test plan.
Matt Pataky owns Sunnyvale Foreign Car Service, 15 Pioneer Way, Mountain View. For more information, call (650) 960- 6988, email [email protected] or visit sunnyvaleforeigncar.com.
