germanturbo
NAXJA Forum User
- Location
- OK / AR
looking for the tach output wire on that plug...
-
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'98 OBD plug wiring diagram, anyone have?
- Thread starter germanturbo
- Start date
anony91xj
NAXJA Forum User
- Location
- North Jersey
germanturbo said:
The tach output would be on the ignition coil's wiring connector, not sure which wire exactly though. If the '98 is direct ignition (don't know what year they stopped using distributors for sure), you may need a tach adapter or something to run a tach or other aftermarket RPM-controlled accessory.
There is no tach output wire on the OBD plug. Those wires all send combined signals to a scan tool. I wouldn't tap into them for any reason.
Why are you looking for a tach signal?
germanturbo
NAXJA Forum User
- Location
- OK / AR
i'm installing aftermarket tach & cruise. Getting to coil wire is no prob. but identifying which wire is neg might be...have continuity to ground with one and no continuity to ground on the other...would the continuity to ground wire be the neg side of ignition coil, then? just don't want to fry any accessories...
I've done this before on jap cars but they always have a little minus sign by the neg side terminal on the coil
thx for the help
I've done this before on jap cars but they always have a little minus sign by the neg side terminal on the coil
thx for the help
5-90
NAXJA Forum User
- Location
- Hammerspace
From 1997XJ FSM (1998 should be similar - they're both OBD-II. Distributorless ignition didn't get started, as I recall, until 1999...)
The problem that you'll have is that the instrument panel is driven by the CCD bus, and apparently not with discrete signals. The two wires on the the coil primary are Dark Green/Orange and Grey. The Grey wire comes from the coil driver signal on the SBEC (Pin A7), and the Dark Green/Orange goes, via a connector and a couple splices, to the PDC, Fuze 20. You could probably tap either one for the tach, but the "ground" side is the switched side, going through the SBEC. You may find it easier to just get a gage cluster with a tach, rather than fooling about with the OEM wiring (OBD can be fairly picky at times...)
Anyhow, the Dark Green/Orange wire should always be hot - to check, disconnect the coil connector, turn the key ON, and check for +12VDC.
There is apparently no Tach signal on the OBD diagnostic connector - however, there are FIVE CCD bus sets (Underhood, Data Link, Airbag Control, Overhead Console, Instrument Panel) there. Unless you've got a smart tach that can decode the IP/CCD bus, you're still going to want to go to the coil wire.
MAKE SURE that there is no power feed out on the tach signal wire, or you have the potential to REALLY screw things up! There should not be, but electronics can be picky...
Was this any help?
5-90
The problem that you'll have is that the instrument panel is driven by the CCD bus, and apparently not with discrete signals. The two wires on the the coil primary are Dark Green/Orange and Grey. The Grey wire comes from the coil driver signal on the SBEC (Pin A7), and the Dark Green/Orange goes, via a connector and a couple splices, to the PDC, Fuze 20. You could probably tap either one for the tach, but the "ground" side is the switched side, going through the SBEC. You may find it easier to just get a gage cluster with a tach, rather than fooling about with the OEM wiring (OBD can be fairly picky at times...)
Anyhow, the Dark Green/Orange wire should always be hot - to check, disconnect the coil connector, turn the key ON, and check for +12VDC.
There is apparently no Tach signal on the OBD diagnostic connector - however, there are FIVE CCD bus sets (Underhood, Data Link, Airbag Control, Overhead Console, Instrument Panel) there. Unless you've got a smart tach that can decode the IP/CCD bus, you're still going to want to go to the coil wire.
MAKE SURE that there is no power feed out on the tach signal wire, or you have the potential to REALLY screw things up! There should not be, but electronics can be picky...
Was this any help?
5-90
5-90
NAXJA Forum User
- Location
- Hammerspace
Well then, I get half marks - if it started in 1999 for the WJ, then it started in 1999, didn't it?
Just kidding - there are a few things I've still not sorted out and filed, and I'd have to check my notes on those. I figured 1999 was "close enough for government work," so it's not a big problem anyhow. I'm fairly sure 1997 and 1998 will be the same anyhow - even though I don't have a 1998 FSM to verify that...
I don't suppose you might have caught anything else I missed? It's a chance to update my notes...
:confused1
5-90
Just kidding - there are a few things I've still not sorted out and filed, and I'd have to check my notes on those. I figured 1999 was "close enough for government work," so it's not a big problem anyhow. I'm fairly sure 1997 and 1998 will be the same anyhow - even though I don't have a 1998 FSM to verify that...
I don't suppose you might have caught anything else I missed? It's a chance to update my notes...
:confused1
5-90
germanturbo
NAXJA Forum User
- Location
- OK / AR
Anyhow, the Dark Green/Orange wire should always be hot - to check, disconnect the coil connector, turn the key ON, and check for +12VDC.
Yes a big help, thx...only prob is i've found the green wire with orange stripe to never yield voltage signal (ign on or off) and to always yield continuity to ground (again, ign on or off)...and that's why I thought it to be the neg wire
the other wire, the grey one, yields voltage with ign on for sure, haven't tried that one with ign off
ok is my truck messed up or something???
Yes a big help, thx...only prob is i've found the green wire with orange stripe to never yield voltage signal (ign on or off) and to always yield continuity to ground (again, ign on or off)...and that's why I thought it to be the neg wire
the other wire, the grey one, yields voltage with ign on for sure, haven't tried that one with ign off
ok is my truck messed up or something???
5-90
NAXJA Forum User
- Location
- Hammerspace
The coil should NOT be powered when the key is in the ACC position, only in START or RUN.
Most coils are ground-switched, which allows them to saturate when the "points" are closed (whaddaya want? I'm old...) When the points open, the ground circuit goes away, and the magnetic field collapses and induces a current in the secondary, creating spark.
I haven't looked at the wiring for the PDC itself, but I'm fairly sure it doesn't have the coild "Hot at all times." It should be "Hot with key in RUN" only - which is why I specified that in your instructions.
If the grey wire is HOT with the connector disconnected, I'd get wiring diagrams for your year (I don't have them handy myself yet. I must correct that oversight...) and check to see what's what. But, you should end up seeing a more-or-less direct connection into the PDC on one side, and a more-or-less direct connection to the SBEC on the other. The SBEC should be on the ground side.
Which is why I'd suggested to disconnect the coil connector, turn the key to RUN, and check for voltage at the coil connector - it's the best way, really. If you leave it connected, you'll probably see voltage at both sides, and that won't help.
Are you sure you can't get your paws on an OBD-II instrument cluster? It would be easier than doing all of this, I'm sure. As I recall, the CCD bus will put out signals to drive all gages, and the IP just ignores the signals it doesn't need...
5-90
Most coils are ground-switched, which allows them to saturate when the "points" are closed (whaddaya want? I'm old...) When the points open, the ground circuit goes away, and the magnetic field collapses and induces a current in the secondary, creating spark.
I haven't looked at the wiring for the PDC itself, but I'm fairly sure it doesn't have the coild "Hot at all times." It should be "Hot with key in RUN" only - which is why I specified that in your instructions.
If the grey wire is HOT with the connector disconnected, I'd get wiring diagrams for your year (I don't have them handy myself yet. I must correct that oversight...) and check to see what's what. But, you should end up seeing a more-or-less direct connection into the PDC on one side, and a more-or-less direct connection to the SBEC on the other. The SBEC should be on the ground side.
Which is why I'd suggested to disconnect the coil connector, turn the key to RUN, and check for voltage at the coil connector - it's the best way, really. If you leave it connected, you'll probably see voltage at both sides, and that won't help.
Are you sure you can't get your paws on an OBD-II instrument cluster? It would be easier than doing all of this, I'm sure. As I recall, the CCD bus will put out signals to drive all gages, and the IP just ignores the signals it doesn't need...
5-90
- Location
- Coshocton, OH
5-90 said:
Thats true the only thing you'll need to have taken care of on a cluster swap is having the ODO changed to reflect the correct mileage for your Jeep. Also IIRC you may, or may not have to change the oil press. sender.
