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Mercury
Grand Marquis
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Check Engine Light Due to Failed Oxygen Sensor on Mercury Grand Marquis

Problem Description and Possible Solution

One or more oxygen sensors may fail resulting in illumination of the Check Engine Light.

Problem Data
RepairPal Verified
Average mileage: 119,905 (89,321–149,000)
5 model years affected: 1992, 1997, 1999, 2000, more2005
20 people reported this problem
Comments
Viewing 1 - 4 of 4 comments
slow to accelerate, runs rough, horrible gas mileage. Hooked it up to system and received engine error code p0171 and po174 cylinder bank 1 and 2.
Gas cap broke and we rode about 10 miles to get new one then check engine light came on started blinking and car started skipping not fixed yet
The check engine light came on and the car runs rough on starting an accelerating and horrible gas milage. When checked came up oxygen sensors needed to be replaced.