Hi all. I've been browsing and searching for the last two days, and this is truly an amazing site. Nice to see such an active and positive community.

I've got a 98 1500 Pickup with the 5.2. I've searched extensively for this and come up dry. There are some mentions of there being TWO Engine Coolant Temperature sensors, but I can't verify that through the shop manual. I was told by a local shop that the truck was throwing the code for that, and it's running terribly, dying all the time in a similar fashion to what I've seen posted on here a number of times.

I replaced the sensor (twice), and can't get the check engine light to go off, or the truck to get back to running properly. It's driving me insane, and I'm planning on trying an IAC Valve replacement on Tuesday, but I'm concerned that the check engine light didn't go off after the ECT replacement, so I'm wondering if there is, in fact, another one somewhere. Rock Auto lists an Engine Coolant Temperature Sensor as well as a SENDER, with different part numbers, but the photos of the units appear nearly identical.

Any help would be greatly appreciated, and thanks for having such a tremendous site.

 

There Is ONE ECT (Engine Coolant Temp SENSOR) But there is also a Engine Coolant Temp SENDER. The Sender is located on the left of the water neck, located near the Heater Hose. (looking at the motor). The Actual computer Sensor is located on the Right of the water Neck , located right under the Air Condition Compressor. Let me tell you, I just replaced that sensor Last week and It was A BITCH to get at. The bracket plate for the Alternator and A/C gets in the way. but it is doable.

As for the sesor and sender being the same , they shouldnt be. The sender is a White Connetor with One wire. The Computer SENSOR is Two Wires. Has a longer Brass Peice as well. Hope I helped , and good luck!

 

I really appreciate the speedy response and great info. I'm going to replace the sender on Tuesday when it's supposedly not going to be freezing cold.

Any idea if they throw the same code, or if the SENDER could be responsible for the vehicle dying on me all the time when it gets up to temp?

Thanks again. Truly appreciated.

 

i thought only obdI trucks had 2?

 

Not to sure, according to my Haynes the Coolant Sensor (the two wire) related codes are PO117-P0119 and p0125 -PO126

PO117 ECT Volt to low
PO118 ECT Volt to high
PO119 ECT Circuit , Intermittent
PO125 Coolant Temp Signal Incorrect
PO126 Insurficent Coolant Temp to Maintain Stable Operation

Let Me Know what CEL (Check Engine Light) you have , and I`ll try to assist as much as possible so that you can get that beast back on the road!

God speed , and Good luck!!!

 

Very Possible, Im not sure on the OBDI , But being 96 , I have OBDII , and If he`s 98 then he`s deffently OBDII and I only have 1 Sensor and 1 Sender.

 

the older models have 2. the later's have 1. idk the cutoff year.
i wouldn't think a bad temp sensor would make it run terrible. it would just run like it does when its dead cold.
you probably have another problem as well. you'll need to try and pin it down. if you can make it run better by lightly pressing the gas, its probably IAC or TPS. if its got nothing to do with the gas pedal, then it could be a number of things, including needing a tune up (dist cap, rotor, plugs, wires) or 02 sensor, or MAP. a good shop with a scanner should be able to tell. or you can just sort of guess, and replace things. sometimes this works. keep you old parts, so that if it doesn't fix the problem, then you've got a known good spare part for the next time.

welcome to DF. fill out your signature in the control panel with your truck info. saves time and typing.

 

Thank you all for your continued involvement. Here's my plan, for the moment:

1. Replace Engine Coolant Temperature SENDER
2. Tune-up (Cap, Rotor, Plugs)
3. Replace IAC

I'm going to start there and see if it solves my problem. If not, I'm going to move on to the o2 sensor (sensors?), thermostat, and throttle body cleaning.

The gas pedal absolutely has an effect on how it's running, but more in the sense of <i>whether</i> it's running. The truck runs great when she's cold, and the engine is strong and smooth. The issue occurs when operating temperature is reached, and is similar to many I've seen posted in the forums: On downshift, the idle dips to below 500rpms, then usually kicks back up. Once it's warm, it can't kick back up and just dies. Dies at stoplights. Dies when switching from drive to reverse, and the opposite.

So, I'm assuming you're right that there's more to this than just the ECT Sender, but that was the last known code so I'm starting there.

I'll update tomorrow for posterity.

Thanks again. You guys are terrific.

 

having screwed around and around with idle problems on my truck, i'd recommend that you skip the tune up for the moment. since its running fine when its cold, its probably not going to help, and a lot of people report broken spark plugs and all kinds of other bad things that can happen during a tune up.

i'd remove the IAC from the back of the TB and gently look at it. don't push, pull, or twist on the plunger. you'll break it. check for gunk on the plunger. gently scrape it clean and spray with carb cleaner as needed. check for gunk in the well. scrape it clean and spray it out as well. if there's not any visbile gunk, then cleaning isn't going to do any good, and i'd just replace it with a new one. keep the old one. more on that in a moment.

if that doesn't fix it, then i'd also replace the TPS. again keep the old one.

without a scanner, its impossible to tell what these sensors are reporting, i've found that its just easiest to swap the parts. you end up wasting some money, but if you keep the old ones that are still good, then you can try them again later. it works for me.

my truck was recently idling high and surging when cold, then dying at stop signs when warm. it seemed like the IAC, but turned out to be TPS.

 

A bad coolant temp sensor WILL make the truck run like absolute crap. I broke one on install once and the ride to the parts store and back was nightmarish.

I had to turn the truck over at WOT to bypass the sensor input. It would bog and die at idle if you didn't keep the gas going.

Try cleaning the O2 sensors as well especially the precat one(s), they aren't read by the PCM during warm up, but are after the truck enters closed loop the PCM starts pulling them for A/F data.