Bad Sensor?

My "Get Engine Serviced Soon" light has been coming on intermittently
since March, and started when it was raining quite a bit. The car is a
1998 4-door SL with 1.92L engine, and about 60K miles. The light would
generally go off after the wet had evaporated from the system, and only
came on during torrential downpours. When I went in for my emissions
inspection I noticed that not only was the light on again in dry/warm
weather, but as I idled the temp and tach would fluctuate rapidly,
though not quite in synch. The temp would go from about mid-level all
the way down to zero and back up in the space of a few seconds. I
failed the emissions test based on the following OBD trouble codes:

P0117 Engine Coolant Temperature Circuit Low Input
P0341 Camshaft Position Sensor Circuit Range/Performance
P0125 Insufficient Collant Temperature for Closed Loop Fuel Control

Driving to the DMV to get an extension on my registration the engine
started racing at a stop light, until I punched the gas a few times.
The RPMs just ramped up suddently and threatened to go off the scale. I
checked the fluid levels and topped off the coolant and oil. Light is
still on.

My question: Could this all be caused by a bad sensor, or is something
more significant going on? Might the timing chain need to be replaced?
Would a tune-up fix things? Some other electrical problem?

Is this a typical pattern, in other words, for a blown sensor?

 

P0117 Engine Coolant Temperature Circuit Low Input

Sounds like two sensors: coolant temp and crank position sensor.

Typicall crank position sensor failures will not lead to the revving
you report but to the engine just stalling. That may be a fluke. I'd
do the coolant sensors (1 or 2 on a 98?) for sure. Oughta help
out your gas mileage too (especially as it seems that your car is
often believing that it has a cold engine when it doesn't).

Tim.

 

Replace coolant sensor. Original may be plastic, the new one should be
brass. If you're due for new coolant, have it done.

Inspect your ignition wires and plugs for the source of the P0341 code.

 

Thanks guys. Is replacement of the coolant sensor something that I can
do myself without a shop full of tools, or should I just have my local
mechanic do it? Or the Saturn dealer?

O.G.