97 Passat VR6 with 96 TDI engine DEQ fail

I purchased a 97 Passat that had an engine swap to 96 TDI. The car is performing fine, but I went through DEQ to get my test results and they failed me based on OBD sensor data: EGR/VVT Unsupported.

I then took the car to my mechanic and this seems to be a pretty rare instance of the chassis having OBD sensor requirements with an engine that doesn't (96 TDI's only need the tailpipe test).

Question: can I "flash" the ECU so that it will see the EGR/VVT sensor and get me up to 97 standards? If so, who can do this?

I have spent hours on the phone with the DEQ, DMV, and my mechanic and we seem to be at a brick wall here. Any help or info appreciated.

Oooh can of worms there. 96/97 was the transition year to OBD-II so your car having a 1997 VIN is being tested under 1997 rules, meaning OBD-II. 1996 TDIs didn't have this. It is illegal to swap in an older engine than the receiving chassis in the first place, so this is one of those unfortunate circumstances of not knowing what you were getting into before buying the car. A 1997 "GQ" or "FA" ECU (suffixes for the VW part number) is a plug-in replacement but may look for other sensors and signals that may not have existed in your 96 harness so it's hard to say whether a simple ECU reflash or replacement would help to pass OBD readiness. On the other hand, the nature of the failure - EGR/VVT Unsupported - may suggest that EGR was simply disabled by the previous owner (VVT - variable valve timing doesn't apply to Diesels).

Contact Jeff Robertson (jsrmonster from Rocketchips) to see if he can help. Oldpoopie is local to you and may be able to help as well.

The 1996 Passat used the BK ECU (black plastic case), which was not OBD-II compatible, but rather OBD-D and very few programs will read the OBD-D protocol. The only EGR difference the 1996 has over the 1997 is the lack of an EGR cooler, otherwise the EGR system is the same with the same functionality.

There was a voluntary recall for the 1996 to swap out the BK ECU for the GQ ECU (silver aluminum case) along with injectors that had a higher pop pressure. The GQ ECU uses the OBD-II protocol and can be ready by any OBD-II reader.

The 1997 Passat uses the FA ECU, which is also OBD-II. The main difference between the 1996 and 1997 is the glow plug monitoring system, which is different between the two. The EGR functionality is the same for both cars.

Using the 1996 ECU in the 1997 or the 1997 ECU in the 1996 will cause a check engine light.

However, it has been documented on here that the EGR reads as "not supported" for the GQ ECU even though it's the same. Here are some readiness screenshots from my 1996 and 1997.






I did a search and found a similar problem to yours here.


You have to go through the Generic OBD2 screen and not through the Readiness screen on the Engine Controller or you'll get this:

Thanks for the feedback!!

I went ahead and registered the car out of DEQ testing to buy me some time, and Jeff from Rocketchips is going to help me update the ECU eventually...

I have the aluminum case ECU, the GQ Bosch version, so it should be available to update.