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Chris (aka - Moose)
Chris (aka - Moose), Technician
Category: Audi
Satisfied Customers: 48011
Experience:  16 years of experience
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98 Audi A6 2.8 , codes p1197 1198 , o2 sensors heater

Customer Question

98 Audi A6 2.8 , codes p1197 1198 , o2 sensors heater circuit electrical malfunction ? Replaced both pre cat sensors , 12v at connector , checked all fuses and relays ? Replaced coolant temp sensor, what triggers ecm to ground or should I say what protocol demands heater circuit activation
Submitted: 1 year ago.
Category: Audi
Customer: replied 1 year ago.
If possible can I check at ecm connector for switching to ground ? What pins do I test ? Or an electrical diagram for o2 sensor heater circuit would be very helpful
Expert:  Chris (aka - Moose) replied 1 year ago.

Welcome, I'm Chris (aka Moose). I normally log in after 3 pm central. Please make sure to let me know exactly what is needed from me so I can provide EXCELLENT 5 STAR service.

Here is that diagram,

Your codes are for 1197 bank 2 sensor 1 and 1198 bank 1 sensor 2.

If your getting battery voltage on the sensors at the red/green wire with the key on then its a broken ground wire or the computer. The computer will ground the wires to run the heaters when the engine is cold to get the sensors up to temp so they can read accurate. Pins 27 and 28 are the ground wires.


On your screen at the top you should see a rating 1-5 stars and a green submit button. Please make sure to select one and press submit. I am not compensated by the website unless a customer rates. Rating only pays me from the deposit you have already made, it does not charge you more, nor close the post. Also all follow ups are free and welcome.

Thanks Chris

Expert:  Chris (aka - Moose) replied 1 year ago.

Hello again Chris here,

1) When customers come to Just Answer the website and the experts want them to have a great 5 star experience.

2) We also want them to be so pleased that they come back for future needs.

3) I have the feeling you were not pleased with my help because the post was not rated and or you need me to help more. If so please do reply.

4) I have an option for an additional fee to upload diagrams, repair guides, find a repair facility, or call you if that would help.

Thanks Chris

Customer: replied 1 year ago.
Hello I'm sorry I did not rate yet, i've been busy and haven't had a chance to test those pins for switching ground, I definitely appreciate The wiring schematics that you sent !! on a sidenote would a mass airflow sensor cause A problem with the o2 sensor heaters? I got a code for the first time the other day , all 4 o2 sensors were replace with new direct fit Bosch , both coolant temp sensor's , and I did it thermostat , on a sidenote is there anything else I should look for ? this car is a complete toilet it has 271987 for Milage !!!! and I told the guy it's not worth fixing !!! When I first got it it had 16 engine codes and I'm down to These now !!! Give me till tomorrow to check those pins and make a deposit in my account , so I can rate , now if the ECM is switching where do I go from there? A good friend of mine that works for Audi said the emblem is your bank account after working on one LOL!!! 0000
Customer: replied 1 year ago.
Secondly I in my Subaru dealer trained technician, worked for the company for 15 years many certifications through them , do you make good money from this? Very interested ? Had a major back surgery a year ago and I'm still not able to go back to work I'm drowning in debt LOL thanks
Customer: replied 1 year ago.
If I find the computer is switching to ground at those pins can I try to run wires directly from the ECM to the O2 sensor's to try to bypass it broken wire in the harness
Expert:  Chris (aka - Moose) replied 1 year ago.

No the MAF sensor will not effect the O2 heaters.

For the prior code you posted those things I mentioned are the only things to check.

Yes you can bypass the wires if needed.