Different thermostat sensor than stock?

[Joeyblaze]

I've got a 1995 gmc k1500 slt. It's got the 5.7 in it and really it runs great. However, it won't pass echeck so I've been replacing parts. This lead me to replace the thermostat sensor, however, when I bought the part from autozone, it Clearly wasn't going to fit into my engine. The one that was in my engine is the

 ACDelco 12551708 GM Original Equipment Engine
Coolant Temperature Sensor

But the one that Amazon, auto zone, rock auto, and Haynes all reccomend is a totally different, two pronged sensor. The harness in my truck fits the three pronged and more circular of the two. I'm just wondering if anyone with a similar truck can tell me which sensor they have and whether anyone thinks that it matters between the two. Once again. The circle sensor is what was in my truck, but the oval one is what every place says is the correct replacement. 

[racetrk]

There should be one on the intake manifold as you’re stating and one on the cylinder head. If that’s what you’re getting when you search “coolant temperature sensor” try searching for “coolant temperature switch” and see if the round one shows up.

[Joeyblaze]

8 minutes ago, racetrk said:

There should be one on the intake manifold as you’re stating and one on the cylinder head. If that’s what you’re getting when you search “coolant temperature sensor” try searching for “coolant temperature switch” and see if the round one shows up.

I've used both terms universally and regardless of what I search the only one comes up is the oval two pronged switch

[Doug_Scott]

What's the build date on your truck?  Have you checked one year older and newer?  Not unusual to have half year changes. 

[Jsdirt]

2 pronged is for the gauge only - 3 pronged is for ECU information.

 

I'd just go on a website like GMpartsdirect, get the part number (usually it's in the head as mentioned - NOT in the intake), then do a general Google search for said part number.

[Tahoe02]

Use your VIN number to check for the correct part.

[riverbanks]

AC Delco 12551708

[riverbanks]

Strange,first time in use on g.m. is 98,f-body,then certain ls motors used the multi purpose sensor,your truck is special