Check engine light?

P0115 †Engine Coolant Temperature Circuit Malfunction

P0420 †Catalyst System Efficiency Below Threshold (Bank 1)

Hi there,

When the check light is on there is a set fault code set in the ECU, you will need to have a scan done to read this code and this will identify the problem you are having.

Mark (Mhpautos)

Not easily. Codes get you to the circuit that needs diagnosis, not usually to the defective part.

Coolant sensors don't fail real often. More common is a loose connector, the connector was removed while the ignition switch was turned on, or a terminal in the connector is stretched and making intermittent contact. The most effective way to troubleshoot them is with a scanner that displays live data.

The rear oxygen sensor monitors what comes out of the catalytic converter. The front one monitors what goes in. By those sensor readings, the Engine Computer knows what the converter is doing. When it's not cleaning up the exhaust properly, it turns on the Check Engine light. Most of the time that means a new converter is needed, but other tests should be done first to confirm that.

How about the heater fan motor coming to a stop?

Perhaps air in the heater core? Radiator fan coasting to a stop? Keep us posted.

Check the engine compression, fuel pressure regulator and ignition timing.
Ensure air filter is not clogged.
Check Engine Coolant Temperature performance.

The coolant temperature sensor should be tested with a simple ohm meter reading before it's replaced. Any goofball can replace parts. Professionals do at least a little testing first to be sure the new parts are needed. If the initial problem started from leaving the radiator cap loose, that's not going to damage the coolant temperature sensor. I suspect someone just unplugged it at one time. Erase the fault codes and see if they come back before replacing parts.

The downstream, (after the catalytic converter), O2 sensor is just reporting what it sees, so changing it isn't going to fix a problem with the converter. Again, see if that code comes back after it's erased.

To erase the codes yourself, disconnect the negative battery cable for a minute, then reconnect it. Don't do this on newer cars because many computers can lock up and will need to be reprogrammed by the dealer. I have to mention that for the benefit of other people who might read this and try it. General Motors and Volkswagen are the worst offenders at that. They are very good at getting your money after the sale.

I've heard that many times before, but more often than not, it's not that you're a women; it's that you don't speak the same language as mechanics. The same can be said of 90 percent of men. As a former instructor at a community college, I was asked almost every week by someone to examine their repair bill, and when it was explained in layman's terms, people realized what at first appeared to be excessive charges was really the mechanic looking out for the customer in the long run.

Many mechanics never even meet the car owner. They just diagnose the problem, then report their findings to the service adviser who contacts the owner with various repair options. Service advisers often don't know much about cars, but they have good communication skills; something most mechanics lack.

We spent a lot of time in my classes too on "perception". A shady salesman for any product can make you feel good while ripping you off. THOSE are the people who give every profession a bad reputation. The honest people in any profession don't make news. We never hear about them.

I felt just the opposite about woman customers when I worked for a very nice Chrysler dealership. I made an effort to do extra things at no charge and to keep costs down to help prove we could be trusted. We had a REAL big base of repeat customers, both for service and new car sales. I was lucky that I often got to meet the owners and talk with them. I explained what their car needed right now and what could wait. We were always so busy, there was no need to try to pad the bill by selling unneeded services. Some shops are slow so they look harder for other things to sell you. That's okay if a preventive service makes your car last longer, but it should really be needed.

We fall into a rut when we explain the same things over and over so we start to leave things out, or we forget you're hearing this for the first time. I've heard mechanics tell a customer what was needed to fix their car, and the way they said it, I wouldn't even approve the service. They are busy and have other cars waiting, and they describe the problem and cure as though they were talking with another mechanic. A good doctor will explain things a lot differently to the patient than to another doctor. Doctors, and mechanics, who are wrapped up in their work, forget or don't want to take the time to explain things in detail. They just blurt out the repair and the cost, and expect you to make an instant, informed decision when you don't have all information. That can lead to the customer's lack of confidence in the mechanic.

The best thing you can do is ask some questions when presented with their findings. Ask if what they found could have caused other problems that might not show up right away. If they give you various choices such as replacing a large component vs. Rebuilding it on site, ask for the advantages and disadvantages each way, and what they would do if it was their car. They might have their own recommendations too. Many repairs involve parts that come as complete assemblies or as individual parts. The individual parts cost much less but take a lot more time to install. Complete assemblies cost more and were assembled in a controlled factory environment, but take less labor time to install. If business is slow, they may opt for the less expensive parts that take more time to install. The overall cost to you might be about the same but it will keep the mechanic busy. If the shop has a lot of people waiting, they will likely steer you toward the complete assembly to save time so they can move on to the next car. Most shops are busy now because people are fixing older cars rather than buying new ones. If you see one shop that has people standing around, there might be a reason. Look for a busy one.

Sorry to get so far off topic. Once I get on a roll, I can't stop.

Is OBDII scanner being used?

The idling speed seems to be too low. Try cleaning the throttle body and IAC.

http://www.youtube.com/watch?v=EzgX5t0qR-8

The above link should be helpful.