Hi guys,

Lately I have been having an intermeitent CEL come on in my '94 Ranger. The code I get is 117, ECT sensor signal voltage too low

The CEL only lights when the engine is under load going up grades after a period of time. If the RPMs go above ~2200 on the grade after a while, the CEL lights. As soon as I come off the grade and the RRMs drop or if I upshift to lower the RPMs, the light goes out immediately.

The ECT sensor was changed about 10 months ago when I had both upper and lower intakes off to replace leaking VC gaskets. I replaced it at this time due to the ease of reaching it with the intakes off and just about every sensor was factory original. Basically so I wouldn't have to replace it in the future with all the crap in the way

Other than a faulty sensor, any other ideas what may cause this DTC? Especially since it only happens when the engine is subjected to higher loads than normal driving?

Thanks

 

Where did you purchase the sensor? Aftermarket sensors are known for there ability to fail fairly quick.

 

AA. Guess I'll just try another one.

 

Just replaced the ECT sensor with a new one. Installed it and still get code 117! I disconnected the battery to reset the PCM. Any ideas what else this may be? Maybe I got a bad sensor?

Truck also has a high idle (1500 rpm) that have I have not been able to resolve. I have searched for vacuum leaks, new PCV valve, and cleaned out the IAC. Unplugging the IAC drops the idle, so it would seem that is fine.

 

Two possibilities:

1) Check the ECT connectior for gunk on the terminals. Spray some brake cleaner on the terminals and put a little dilectric grease on them as well.

2) If you have a multimeter, check for a galvanic charge in the coolant.
Set on voltage, place one lead in the coolant and the other to ground. Technically, above 0.500 volts is bad. If you find a galvanic charge.... flush the coolant.

Rich

 

Thanks wydopnthrtl

I'll give both a try. I have seen alot of your posts in the political forum and I just now figured out your screen name, lol.

 

LOL.. I like lots of things on the "right". Plolitics, religion, throttle....

 

wydopnthrtl

I took the connector off and used some brake cleaner and a can of compressed air to clean out the contacts on both the connector & sensor.

I then checked the coolant with a DMM. With the negative probe in the coolant at the radiator cap and the positive probe at a rusty bolt going through the core support I got an average of 0.4 VDC. I checked it numerous times and sometimes I would get 0.5VDC or greater, but usually ~0.4VDC.

After I reconnected the battery, I warmed the engine up and got a pass (111) on my code scanner. We'll see if the code returns. My mpg has been diminishing, could this be from the PCM enriching the fuel mixture?

Truck also bucks sometimes when I let off the gas (M/T), related issue?


Same here, lol

Thanks for all your help.

UPDATE:

Well I took the truck for a drive and as soon as the engine went under a heavy load, goining up a hill, the CEL came on again. I have yet to understand why the CEL only lights when the engine is under a heavier load or if I shift above 3500 RPM. This is really starting to get annoying.

 

I wouldn't think that would cause a buck? The timing and fuel maps don't do that to an engine.

Also, there are two temp sensors on most engines. One for the dash and one for the PCM.

If the volts are that high you might try flushing it and remeasure / re-clearing it.

Otherwise.. I don't know?

 

About the bucking, I just wasn't sure what to expect. I'm going to run some cleaner through the coolant system and then do a flush. I changed the sensor for the PCM, the one at the front of the lower intake. I was thinking that the CEL probably only lights at higher engine loads/RPM's due to the coolant flow being higher at that point, just a guess.

Thanks Rich, I never would have thought about galvanic charge in the coolant. Changing the coolant may not resolve the issue, but it can't hurt either.

 

Well, I had the radiator flushed today. I am still getting code 117.

New sensor
Cleaned electrical contacts
Flushed cooling system
Checked wiring at the connector for enough slack

I'm not sure what else to do at this point. Now that cooler weather has set in, the truck won't run in the morning unless it's warmed up. If I try to drive before it warms up, it dies out and is hard to start afterwards.

Is there anything I'm missing here or other parts to test?

Thanks

Bill

 

Fixed the code for the ECT. After doing a bunch of troubleshooting with a DMM and cleaning the PCM connector and pins, the code is gone. The bolt holding the PCM connector to the PCM seemed a little loose as well.

The stalling issue was resolved with two new relays, one for the fuel pump and the other for the PCM.