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05-11-2013, 08:59 PM #1
- Join Date
- May 2013
95 Yukon - Weird Coolant Temp Sensor (to ECM) Issue
I recently blew a TBI gasket, so I decided to bite the bullet and clear out my trucks "to-do" list.
I had codes 22,32,35,54 stored in the computer before the work, and the MIL would come on every so often while driving and turn off after a minute or two. I've owned the truck since '08, and have put roughly 70K on it. (At 264K now)
I replaced the TBI mount gasket. I cleaned out/degunked the TBI assembly. I replaced all the gunked up vacuum lines between the TBI and EGR, PCV, etc. I replaced the EGR valve and the PCV. EGR solinoid is 2 years old. IAC is a year old. I cleaned the IAC, but it wasn't that dirty. Replaced the ripped air inlet pipe, as well as the air filter. (eventually replaced both the coolant temp sensor to the ECM, and the pigtail)
Overall the truck runs better than it ever has, except for the transition between idle and light acceleration, where it bogs severely. It did not do this before the work. The truck will run OK when it gets to speed, or at idle. I also now have a solid on MIL with codes 14 & 15 (Coolant Sensor Circuit Shorted & Coolant Sensor Circuit Open).
After replacing the sensor (TS4052 from Napa), I checked it for proper operation. I measured it from 800 Ohms down to 200 ohms while the engine heated. Same issue of bogging on light acceleration, MIL on.
5V is present on the pigtail, ground appears solid. I replaced the pigtail just to be sure, same issues.
The strangest part is that if I put a 470 ohm resistor across the pigtail, the truck runs fine and the MIL turns off. Slightly rough at times, but overall no hesitations or bogging on a 7 minute trip to the auto parts store. Could I have bought a bunk sensor? ECM toast? Other thoughts?
I can live with keeping the resistor in place for the short term, but I am absolutely out of ideas on the sensor short of buying another one...even though this one appears OK on the multi meter.
Appreciate any advice you can give.
'95 GMC Yukon 5.7L 4WD 2DR
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