Check engine light on mabey bad ground wire?

[gabegt90]

Well today when I was driving to school The check engine light came on. so I thought to my self it's most likley the ground wire the is connected to the back lower manifold bolt is this what is could be causing the problem? or do you think something elese Mike was telling me that its the ground to the o2 what do you guys think thanks? mangs

[LtMercDaddy]

My light only comes on under 2 conditions that i have seen, LOW oil press, or High Coolant temp. Well it used to come on with high coolant temp but no more due to aftermarket guage. yours merc is newer so it probably comes on for all kinda goofy shit....

[Tiggie]

I think 89 still had the goofy oil pressure-high coolent temp gauge.

Check oil and coolent levels. Replace senders and hope for the best. Might also test the oil pressure and water temperature with aftermarket gauges. I know personally my engine has been hot enough to puke out much of it's antifreeze because it was so hot. The temperature light never came on. These things gotta be roasting when the temp light comes on. I now have an aftermarket gauge.

[gadget73]

What they said. I call that the 'replace engine' light because usually if it comes on for real, the motor is kind of fubar. I think the overheat sensor trips at like 250 or something crazy, and the oil pressure trips at like 2 psi.

[mrltd]

Where is the stock temp sender wire? Since you put the aftermarket gauge in. It could just be that we moved the wires around and the stock temp wire is grounded and will turn the light on.

[gabegt90]

mabey I'll check on that I'll let you guys know