TPS testing help!!

Per the FSM I'm supposed to hook my voltmeters negative lead to the "D" terminal. Problem is, on the two harnesses connected to the TPS, neither of them have a "D" terminal. I have two sets of "ABC". what to do??

EDIT: oh yeah, 88 XJ 4.0 w/ the multipoint EFI

twardozrally said:

Per the FSM I'm supposed to hook my voltmeters negative lead to the "D" terminal. Problem is, on the two harnesses connected to the TPS, neither of them have a "D" terminal. I have two sets of "ABC". what to do??

EDIT: oh yeah, 88 XJ 4.0 w/ the multipoint EFI

Click to expand...

My '89 uses a 3-prong flat and 4-prong square plug. The latter has a blocked-off terminal. I think the flat plug is for the TCU and the square is the MPI ECU.

As long as you can determine which plug is for the ECU, it's not too hard to probe with DVM to figure out sensor ground, +5Vdc supply and the returning voltage based on throttle position.

An 88 wiring diagram I have indicates - brown = sensor ground, light blue as +5Vdc and yellow/green as reference voltage input. My '89 is a little different color coding and I've heard about some weirdness with my manual before. However, it's just a potentiometer so it made sense once I got into the sensor and it's function. Can also be checked with an ohm meter directly on the pot disconnected from the wiring harness.

Actually, the flat plug is for the ecu/F.I.- go look at a manual trans. XJ.
The middle pin is the ground for testing.

ren said:

Actually, the flat plug is for the ecu/F.I.- go look at a manual trans. XJ.
The middle pin is the ground for testing.

Click to expand...

The manual never states the ECU is the square plug but that is the plug it indicates to use for adjustment. Because of that, I've always assumed that the square plug is for the ECU but it could be either one I guess? The OP never gave transmission type but with two connectors, I would assume it's an auto. Here's the auto tranny procedure from the FSM I use:

I can't remember the colors off-hand, but they are they same for both, so the middle pin in the flat plug will give the colr for the neg. in the sqaure. I am not sure by "D" pin but, I think it is not the blocked pin.

ren said:

I can't remember the colors off-hand, but they are they same for both, so the middle pin in the flat plug will give the colr for the neg. in the sqaure. I am not sure by "D" pin but, I think it is not the blocked pin.

Click to expand...

They are only the same color for both at the sensor side on my '89. Once the connectors reach the wiring harness, the color coding changes. Yes, pin D is not the blocked terminal on the square connector.

Anyway, I hope the OP can describe if they have both flat plugs or a square one. The '88 could both be flat and I know the FSM's disagree about some of this TPS stuff.

My 88 ltd has both flat and square plugs, BUT, this a jeep we're talking about. I don't think even the FSM and engineer crew even knew what was what most of the time. LOL