so I was rounding off the little wiring bugs I have and found my temp gauge doesn't work in my 4.9. I've looked at mickeys wiring thread but my tps plug doesn't have the same colored wires. Mine are black, blue and grey and it seems my temp sender grounds thru the unit.

when my sender isn't grounded to the engine the fan kicks on, also I have tried every combination and used a lighter to test the sender to the gauge with no results. It is possible that the gauge is malfunctioning but it did work before the swap.

is there anyway to test the sender out of the car with a DMM?

thanks for any help

The Black, Blue and Gray TPS sensor is a throttle position sensor

+5v on the Gray
Blue - signal to the ECM
Black Ground.

The CTS sensor for the ECM is a yellow/Black wire. Most likely your CTS is only a two wire sensor and does not support a gauge. You can swap to a three wire CTS from a 3800 and use the third pin to run your gauge.





The black and yellow wires from the ECM connect to the top two pins of this CTS. The green gauge wire connects to the bottom pin (and grounds through the engine) The two functions of this sensor are totally independent but are housed in a single unit.

Two wire CTS sensor connector

[This message has been edited by phonedawgz (edited 01-06-2012).]

ya that's what I did, I swapped out the 2 pin for the 3 pin and am using a tps plug. Black went to black yellow went to grey the one next to black and blue he bottom lone wire on he tps plug went to brown that is on the c500. I connected the CTS to engine ground and put a lighter to it with the key in the power on but engine off position but am not getting any readings.

You can check your wiring by just grounding the wire that runs to the temp gauge. If the gauge pegs (key on engine off) then you are working with the right wire to be connected to the middle pin, and the wire.

I grounded it and nothing my fan does come on when its all 3 wires are not grounded tho, also for some reason my oil pressure light comes on then my check engine light when ground them. I'm gonna have to go over the 84 wiring pdf and see what I did wrong. Clearly the c500 wire I connected it to isn't the temp wire.

Agreed

i had it hooked up to the idiot light and not the gauge thanks phonedawgs