P1187 Oxygen Sensor Heater Circuit Short Upstream-thats my problem for my check engine light, im not sure where to start looking on my 96 5speed to find the problem. does it have anything to do with the O2 sensor? (is it the O2 sensor?) spark plugs?, or is it something with the catalysts? (im lost) also is this sensor or whatever important? thanks, all help is appreciated

 

Yes, it is for the O2 sensor. Disco's use heated O2 sensors to get them to operating temp quicker. Between the exhaust manifold and catalysts, you will find what looks like a thick bold screwed right into the exhaust pipe. Them are the O2's. If the wiring and connections all look good and tight(and not corroded), you probably have bad O2's.

 

thank you very much

 

Forgot to add, they will have a 4-wire lead coming out of them. If you have a multi-meter, check resistance between the red and white wire on the O2's themselves, that is the heating circut.

 

The O2 sensors are an integral part of the system which controls air / fuel mixture. So, they are very important. Your model has four O2 sensors. For this test you will only need to be concerned with the two forwardmost sensors, before the cats.

If the heater circuit is bad it is not necessarily the end of the world. The sensing part of the O2 will still function and send signals to the ECM, just not as efficiently. Perform Kenk's suggestion and test the heater circuit wires. If you find there is no ohm reading ( no resistance value = open circuit = bad sensor) then replace them both and not just the bad one.