Oil pressure sender 98 vs 99

Can anyone explain why/how the oil pressure sender on the 98 is different from the 99? I was surprised to see they have different part #'s on Rock Auto. Comparing the wiring & connector diagrams across the FSMs, they appear to be identical.

I mean, the thing just takes a pressure and converts it to a voltage, it seems very odd that this part would change when very little (if any) of the electrical stuff changed between 98 & 99.

Of course I'm asking because (a) the 98 sensor seems to be a good chunk more expensive and (b) I'm getting strange randomly bouncing readings from a brand new sensor, so I'm wondering if the wrong year was put in the wrong box.

The differences are strictly physical.

RCP Phx said:

The differences are strictly physical.

Click to expand...

Physical in that they operate differently? I mean, they definitely LOOK different.

No electrical differences(not sure of a pin-out change).

pinout is the same assuming the FSM is correct.

Well the plot thickens. I had completely forgotten that the oil pressure sender on this particular 98 XJ is a 2 wire. The FSM makes no mention of this, although the 97 FSM shows a 2 wire oil pressure sender. This XJ is a 2WD, but the FSM makes no distinction there.

This jeep is a single owner and there is ZERO chance somebody replaced the harness or anything crazy like that. Is this a known thing on 98s, or do I maybe have an early 98 that still had some 97 artifacts? I have another friend with a 2WD '98 who is going to look at his wiring later today.

I have a "new" computer coming for a 2WD '98 (the existing computer died somewhere during our engine swap). We've been using a 99 PCM (which works GREAT) but it's expecting a 3 wire oil pressure sender so we don't get a reading at the gauge cluster. The new 98 computer shouldn't resolve this issue according to the FSM. I know how to fix the wiring to make a 3 wire work, but I'm left wondering what other things might be subtly different?

I have another friend with a similar 2WD 98, and he also has a 2 wire oil pressure sender. HIs production date is May 98, so I wouldn't think that artifacts from 97 would still be present that late in the production run. That leaves me to wonder either (a) are all 2WD models using a 2 wire oil pressure sender or (b) is the FSM wrong, and *all* 98's use a 2 wire oil pressure sender? Or (c) something else entirely.

What '98 FSM are you using? (Don't link!!, just publisher and year(s) covered).

I have a '97 and '99 but no '98. The '97 shows a 2 wire sensor, the '99 shows 3 as you noted.

The pics of the OP sensor on RA do show 2 pin ('98) vs 3 (pin '99). The '97 shows 2 pins but are round vs flat pins on the others.

Saudade said:

What '98 FSM are you using? (Don't link!!, just publisher and year(s) covered).

Click to expand...

I found it online, it came as a zip which extracted each section into its own document. So I don't KNOW that the 8W section is for a 98.


.......I just checked the folder structure, and SONNUFA---- it's labeled 99. Back to the hunt for a 98 FSM. I'm primarily a TJ guy, and the TJ forum I live on has a resources section with all these documents freely available. I'm wondering why the XJ community doesn't have the same thing.

Ok, found the 98 FSM on Scribd. Trial membership got me the download. The oil pressure sender is still shown as a 3 wire. Here's the connector, it doesn't look like the one in the 97 FSM either.

/Users/craignelson/Library/Messages/Attachments/58/08/7B392804-98B9-4504-85CC-76831CC2365B/IMG_1994.jpeg

whoops, thought that would paste in like on other forums. NOPE!

No worries. Rules say no posting links to FSM!! See the sticky at the top of the forum.

Your link is to your PC. You can just edit your message and delete it.

I couldn't find the edit button but the link was to a photo of the connector that doesn't match what I find in the FSM.

(as an aside, I just wonder why the TJ forums have sections dedicated to sharing FSMs and the XJ forums seem to want nothing to do with them, just an observation.)

Le sigh. Apparently the build date on this guy is 9-97, so it's completely possible I have artifacts of a 97 harness. "New" 98 computer should be here this week. If it doesn't work, I'll just hack the harness to make a 3 wire oil pressure sender work.

Welp, the new to me 98 computer resulted in a crank/no-start condition. I guess we're going with the 99 computer & will modify the harness to use a 3 wire oil pressure sender.

So much about this doesn't make any sense, but it doesn't look like there are too many answers out there.