U1991 Engine Code Repair

Meaning of U1991 engine trouble code is a kind of network trouble code and U1991 code can be about replacing a broken oxygen sensor can eventually lead to a busted catalytic convertor which can cost upwards of $2,200. Taking your car into a shop will cost you around $210 depending on the car. However, an oxygen sensor is easy to replace on many cars and is usually detailed in the owner's manual. If you know where the sensor is, you only have to unclip the old sensor and replace it with a new one. Regardless of how you approach it, you should get this fixed right away.

U1991 Fault Symptoms :

U1991 Possible Solution:

Excessive air inflow can be caused by a vacuum leak, a dirty sensor or, an exhaust gas recirculation valve not closing properly. If the problem is not enough fuel, the culprit may be dirty injectors or fuel filters, a weak fuel pump or a leaky fuel pressure regulator. The lean fuel mix error may be accompanied by rough idling, engine misfires, hesitation during acceleration and overall poor engine performance.

U1991 Code Meaning :

The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate.

Parts or components should not be replaced with reference to only a U1991 DTC. The vehicle service manual should be consulted for more information on possible causes of the fault, along with required testing.