Question

When my 1999 Mercury Cougar V6 2.5L gets hot, the engine lite come on with code P1151

Answer 1

Hi there

This code is for a lack of O2 sensor switch. This generally means the sensor is stuck either lean or rich. This shouldn't have anything to do with the engine running hot unless there is a problem with the head gasket leaking coolant.  This does indicate a possible problem with the engine, but not the cause of the overheating. It could also just be a faulty O2 sensor.

Answer 2

P1151 Mercury Code - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2
Read more: https://www.autocodes.com/p1151_mercury.html