'01 Buick Le Sabre SES Light On

Bob Villa wrote in news: snipped-for-privacy@googlegroups.com:

Please give the actual alphanumeric codes, not the text descriptions.

Codes are a letter followed by four numbers (sometimes also letters as well). Example: P0301.

P0128

Bob Villa wrote in news:3e19fda0-bf91-410a-9c6c- snipped-for-privacy@googlegroups.com:

You gave three errors originally, but only one code now. How come?

That's all the print-out gives...and then the possibilities of fault.

Thanks to the OBD II, you should be able to solve this problem in 20 minutes or so. :-)

OTOH, are you having any other symptom than the service engine light being on? If there isn't, I'd reset the light and see if it gets another error code gets trapped. Sometimes the don't come back.

After taking a trip the MPG is 20% or so worse...and I would need the scanner to reset the fault. I think I will change the stat ($8.50) and then the sensor ($18.50) if needed.

Maybe if you learned about real diagnostics using a good scan tool you would have repaired the problem in less than 30 minutes.

Customers initial complaint - Check engine light on and decreased fuel mileage. (probably low heat as well but may have not noticed)

Put scan tool plug into the port turn on key and run a scan.

Code says - P0128 = Engine not coming up to full operating temp. No other codes (at least none that the code reader they used show)

Possible causes (as any P0XXX is a generic OBDII code)

Low coolant Bad thermostat Bad ECT Cooling fan relay failure (fans on constantly)

From inside the car -

Pull the freeze frame data and it shows the engine had been running for

138 minutes, at 2,100 rpm, at 53 mph and engine load of 12% with a coolant temp of 161 degrees when the code was set (there will be more data but that coolant temp vs run time and load are the ones you need to see for this code.) Normal coolant temp under those conditions would be 210-220 degrees. Yep it's running cold. WHY?

A bad ECT will set one or more of the following codes -

P1114 - ECT Sensor Circuit Intermittent Low Voltage (sensor/wiring shorting to ground)

P1115 - ECT Sensor Circuit Intermittent High Voltage (sensor/wiring shorting to 5 volt reference)

P1116 - ECT Signal Unstable Or Intermittent (sensor/wiring faulty)

P1117 - ECT Signal Out-Of-Range Low (Thermistor failing with increased resistance)

P1118 - Engine Coolant Temp Signal Out-Of Range High (Thermistor failing with decreased resistance)

P1119 - ECT Signal Out Of Range With TFT Sensor

These are all available on a good scan tool and point directly to the problem. Either the wiring or the sensor unless they used a cheap code reader only and not a scan tool capable of OEM specific codes and didn't get ALL the codes.

Go into bi directional control and cycle the cooling fans. They cycle on/off OK

So it isn't the fans or ECT sensor causing the code.

Open hood. Smell for excess gas, pull dipstick to make sure no gas or water in oil. None noted. (Why, because another possible reason for poor mileage and a cool running engine could be a leaking injector causing a rich mix. Usually this would also set a code but it never hurts to check. Water check because a leaking intake or head gasket could be dumping water into the engine causing a low coolant condition.)

Nothing found. Check coolant level in overflow - OK, Check actual coolant level in radiator - OK

Most likely fault - Bad Thermostat - Failed fully open.

Notify customer - outline possibilities for repair.

Drain coolant - replace thermostat - refill

Coolant flush (if system shows signs of low maintenance and low coolant concentration) - new thermostat and refill.

Steve, thanks for being so understanding (as always)...you will note in the original post "85K,2nd owner-with moderate knowledge"!

Not a problem. Sorry if it sounded like I was yelling at you. The diatribe was for dsi1, who for some reason thinks that using a scan tool to do diagnostics is a foolish thing.

I don't do the "clear the code and see if it comes back" on any customer cars. Just isn't worth the hassle of bad word of mouth.

Are there sometimes spurious codes, Yes. Most of them become known over time as well.

I can appreciate your structured approach to weeding out the problem. If you're a professional mechanic, you should follow a well thought out protocol.

OTOH, it it was my car, I'd just reset the light and see if it happens again. My guess is that there's nothing wrong with the fuel injectors and that the loss in gas mileage is due to cold weather i.e., it's a red herring. The reality is that we need more info on this problem.

You might think it's fine and dandy to change parts on a car that has no issues other than the check engine light being on but I've never operated like that. At the very least, I'd like to be able to replicate the problem. I leave the throwing of random parts at a car to the professionals. (-:

Put a piece of electrical tape over the light.

If I replace both parts for about $25...I can break even after a few tank fulls! 34 vs 26 MPG is a great savings!

Or you could buy a used Yamaha Zuma 125 for $1,500, and get 90+ mpg.

And how would that work with 3 kids and a wife?

Better - you get away from them!

Bob Villa wrote in news: snipped-for-privacy@googlegroups.com:

You put everybody on the same bike. That's what they do in India.

piece of cake:

No the reality is that the tests showed the problem as a bad thermostat and resetting the light isn't going to change that.

Checking for excess fuel is simply to rule out any other potential causes. Part of actually diagnosing the problem and repairing it. As I said an injector problem should show a code but I've seen them leak and not show anything.

No, A professional would actually repair the car regardless of who it belongs to.

The only part that needs changing is the thermostat.