How can I by-pass the temperature sensors in the catalytic converter

Mliston5

Member
Joined
Mar 18, 2012
Location
Columbus, Ohio
TDI
2005 Passat TDI and 2011 Jetta TDI Sport wagon
I remember reading somewhere that adding a couple of resistors to the wires for the temperature sensors will fool the computer into believing the sensors are fine. I cannot find the information now. Does anyone have any suggestions?

Thanks
 

GTiTDi

TDIClub Enthusiast, Macht Schnell! Vendor , w/Busi
Joined
Oct 18, 2010
Location
3 Spruce st Wareham, gateway to Cape Cod Massachus
TDI
'91 GTI CJAA swap,'02 Jetta wagon ALH swap, '03 GTI 1.8T rally car, '03 Sprinter 3500
I remember reading somewhere that adding a couple of resistors to the wires for the temperature sensors will fool the computer into believing the sensors are fine. I cannot find the information now. Does anyone have any suggestions?
Thanks
keep searching, the info is there:)
 

Mliston5

Member
Joined
Mar 18, 2012
Location
Columbus, Ohio
TDI
2005 Passat TDI and 2011 Jetta TDI Sport wagon
Thanks, I am putting the car back together today so I'll just plug in the sensors and see what happens.
 

Jack Frost

Veteran Member
Joined
Nov 30, 2007
Location
Rural Manitoba
TDI
2009 Clean Diesel
I am surprized at what jackgreen's results. I would expect that if the car's computer sees no change in values from the DPF's sensors, the computer will declare the DPF defective.
 

compu_85

Gadget Guy
Joined
Sep 29, 2003
Location
Springfield VA
TDI
... None :S
It isn't a dpf... we're talking 1988 technology here. The computer on that car isn't very smart. The sensors are not used for anything anyways.
 

Mliston5

Member
Joined
Mar 18, 2012
Location
Columbus, Ohio
TDI
2005 Passat TDI and 2011 Jetta TDI Sport wagon
Thank you all for the advise. I cleaned out the converter and put the sensors back in. The car runs fine and so far, no check engine light.
 
Joined
Nov 11, 2005
Location
Somerville, Massachusetts
TDI
98 Jetta, Black
I got my exhaust rebuilt at a TDI friendly shop. The mechanic asked if I had any check engine lights, which I didn't. He then correctly guessed that I have a Rocket Chip, because I was missing both temperature sensors.

He told me that that will throw a code normally, but RC gets rid of it. This may explain why some people get codes and others don't.
 

TonyJetta

Top Post Dawg
Joined
Sep 15, 2005
Location
Tucson, Az
TDI
'15 Jetta TDI SE / '06 Jetta TDI DSG Pkg0 / '96 Passat TDI
The GQ ECU for '96 ignores the sensors and the 5th injector. The BK ECU requires them to be functional.

IIRC< the GQ ECU does look for the sensor: It just doesn't use them. Does that make sense? Think of it like this: The ECU is making sure the light works, but doesn't turn on the light.

Tony
 

_Christ

Veteran Member
Joined
Jan 25, 2014
Location
Gillett, PA
TDI
1996 Passat TDi
Randomly came across this, but I have a GQ ECU in my '96 and both the 5th injector and the cat temp sensors are present and working... I plugged the 5th injector and have a ripped wire on the after cat sensor and I'm seeing a CEL for the temp sensor that I have to resolve eventually [using the resistors].
 

big dipper

Member
Joined
Sep 24, 2016
Location
oregon
TDI
mk2 1Z TDI
i have a 96 1z tdi in my mk2 jetta and i have a "GQ" ecu and my car still has a check engine light. you can turn the key to the on position and pump the throttle pedal 6 times or so and it will flash check engine light code 1414 which is for exhaust temperature sensor . my question is why am i getting a check engine light when the fifth injector is not suppose to be programmed in this ecu? is there a way to vagcom this out?
 

Windex

Top Post Dawg
Joined
Apr 1, 2006
Location
Cambridge
TDI
05 B5V 01E FRF
Can't VCDS it out, you need to either:

a) get a tune that ignores the sensors, as above

b) find the harnesses for the temp sensors and run a resistor across then to foll the ECU into thinking that the sensors are still there.
 

Matt-98AHU

Loose Nut Behind the Wheel Vendor
Joined
Apr 23, 2006
Location
Gresham, OR
TDI
2001 Golf TDI, 2005 Passat wagon, 2004 Touareg V10.
i have a 96 1z tdi in my mk2 jetta and i have a "GQ" ecu and my car still has a check engine light. you can turn the key to the on position and pump the throttle pedal 6 times or so and it will flash check engine light code 1414 which is for exhaust temperature sensor . my question is why am i getting a check engine light when the fifth injector is not suppose to be programmed in this ecu? is there a way to vagcom this out?
The GQ ECU merely doesn't actuate the pump for the 5th injector. So, while it effectively is disabled with that ECU it still monitors for the pump itself as well as the catalyst temperature sensors. You will have to leave them installed or wire in resistors to fool it into thinking they're still installed. I used a couple 220 ohm resistors to emulate the temp sensors.

OR, you can swap to the FA ECU from the 97 Passat that doesn't monitor for any of that, BUT, the problem there is you would have to rewire the glow plug system. The FA ECU has diagnostics for the glow plugs and uses a completely different relay to accomplish it, located in a different slot with different wiring. The GQ and BK ECUs use a dummy on off relay, no diagnostics, so they don't know if you have a bad glow plug or not...
 

big dipper

Member
Joined
Sep 24, 2016
Location
oregon
TDI
mk2 1Z TDI
The GQ ECU merely doesn't actuate the pump for the 5th injector. So, while it effectively is disabled with that ECU it still monitors for the pump itself as well as the catalyst temperature sensors. You will have to leave them installed or wire in resistors to fool it into thinking they're still installed. I used a couple 220 ohm resistors to emulate the temp sensors.
OR, you can swap to the FA ECU from the 97 Passat that doesn't monitor for any of that, BUT, the problem there is you would have to rewire the glow plug system. The FA ECU has diagnostics for the glow plugs and uses a completely different relay to accomplish it, located in a different slot with different wiring. The GQ and BK ECUs use a dummy on off relay, no diagnostics, so they don't know if you have a bad glow plug or not...
WOW thank you. this was the most informative reply i have had. guess i will fool it with some resistors till i buy a chip
 
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