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My first CEL
obradley48 - 8 months ago
I searched this forum and didn’t find the answer to my question so please forgive the posting of something that has been beat to death...

After hard acceleration my CEL came on when I got home the OBDii reader found a P1121 code. My reader doesn’t have Porsche listed so I used VW/Audi. Reader said “O2 sensor heater circ. Bank 2 Sensor 2 Short to ground” cleared the code and went for a short drive CEL did not come back on, but checked again and now the same code is pending.

After some research- it appears that a Porsche P1121 code refers to the TPS.

Can someone clarify this?

I do have a FabSpeed Supercup exhaust on the car- would that affect the O2 sensor reading?

1999 Boxster 2.5L

Edited 1 time(s). Last edit at 05/02/2021 07:17PM by obradley48. (view changes)
After more research I found a 9yr old thread on this forum with the Porsche codes. So I understand that it is O2 sensor not the TPS.

Also saw that Pedro said not to freak out about codes. There was also a very funny response saying what codes SHOULD say lol!

Basically “Hey your O2 sensor wasn’t happy”...again...
The exhaust won't affect the O2 sensor readings unless you also changed the cats. This code means that the O2 sensor heating circuit is not functioning properly. It could be the electrical circuit, the connector, or the sensor.

I would start by checking fuse C2 (oxygen sensor heater power), then checking that the electrical plug is corrosion-free and seated properly. Then I would test that the O2 sensor heating wires (pins 1&2) are connected with a small amount of resistance (probably under 10 ohms). Then I would test that the car is supplying 12v to the heater circuit by unplugging the sensor and testing the voltage between the heater circuit pins (1&2) to verify battery voltage (12-ish volts).

Edited 2 time(s). Last edit at 05/03/2021 02:27PM by Boxsterra. (view changes)
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