Reading EGT on VW TDI Passat

Having trouble reading the Pre Turbo EGTs on the 2004 Volkswagen Passat. None of the EGT PIDs (1-13) have any kind of data showing. Do I need to add in a custom PID?

EGT:s are not read by the default OBD2 configuration. You need to make your own XML description file to add those PIDs into the rotation. You can find the default XML and some instructions here:

I have added this to the rotation:

I am getting the PID to show up as an option in ECU Specific but am not getting any data. I have been able to read the intended data with a separate VW specific tool (VCDS group 74) and can see that the ECU is sending this data on the network. What would you do for the next step in troubleshooting?

If you go to OBD2 monitor and issue that command (0178), what do you get as a response?

Getting this output from running 0178:


Hmm, that does not look exactly right to me.

Reply decoded as RealDash interprets it:

Reply header info

This should contain the info on what request this reply is related to. When RD sends 0178, this should contain 4178 to indicate valid reply. Actually, per documentation 7F indicates a PID request error.

Value data. With your conversion this should result 423, which seems like a reasonable EGT value.

I agree the somewhere in the 400s is an appropriate reading. However, I get a constant reading of 32 on the gauge like there is no data being read.

I did some tests on the simulator on how to handle this. As I said, reply should contain 4178 to indicate that its a reply to 0178.

I will add a special code path to OBD2 parser to retrieve the data even if expected PID reply is not found. I think its still better than getting nothing.

Thanks for all your help. After this is added what are my next steps to test in vehicle? Is there an app update cycle that needs to happen first?

I can provide you with test version for Android. Send me an email to