Wiring a high idle switch?

[JEEPZZ]

Here's some info regarding the computer wire connection to be used for the extended idle setup:

EXTENDED IDLE SWITCH TEST
OPTIONAL POLICE PACKAGE ONLY
The extended idle switch is used to raise engine idle speed to approximately 1000 rpm when the auto shifter is in either Park or Neutral position. A rocker-type switch (extended idle switch) is mounted to instrument panel. This switch is available only with 4.0L engine when supplied with optional police package.

The extended idle switch will control a ground circuit going to the powertrain control module (PCM) When a ground signal (through the switch) has been received at pin/cavity A-12 (circuit K78) of the PCM, engine idle speed will increase.


For 1984-1992 I6 XJs and all I4 XJs:
Not an option in computer pin-out.

For 1993-1995 I6 XJs:
PCM Pin # 10, Purple, [60-pin connector] (Switch On: 1V, Off:12V)

For 1996 I6 XJs:
PCM Pin # 12, dark blue/orange, [Black "A" 32-pin connector] (Switch On: 1V, Off:12V)

For 1997-2000 I6 XJs:
PCM Pin # 12, gray, [Black "A" 32-pin connector] (Switch On: 1V, Off:12V)

Switch location for 97+ (optional 4 opening switch bezel)

 

[scoobyxj]

JEEPZZ, do you know when just grounding pin #12 if the ECU does the thinking for the rpm raise when in park or neutral, or is there something in the switch that only activates it when in P/N. I have a FSM for my 2000 that I've been looking at, but as you know they're not always exact.


Oh, if anyone has, or can get one of these I would be interested in taking it off you hands.

 

[Tim_MN]

This one is from (I think) a 94 XJ. It was mounted in the dash on the left of the steering wheel. The other non-cop XJ's just had a blank area with the outline of a switch.
.

 

[Tim_MN]

Somebody PM'd asking about part numbers on the switches and bezel. I might be wrong about the year of the Xj or the parts were just carried over from earlier. The bezel has AMC and the AMC logo on the back side. Bezel P/N 55001893. Ext idle switch P/N is 56000025.
.
EDIT........They appear to be valid and current P/N's

Item Number MSRP Core Price Price
55001893 $5.35 $0.00 $3.68

HOUSING, SWITCH





Item Number MSRP Core Price Price
56000025 $33.35 $0.00 $23.00
Electrical - Chassis electrical - Switches - Fog lamp switch
FOG LAMP SWITCH, MJ, XJ Series 1992 - 1996


Part Number Search Results : Collision Catalog

Item Number MSRP Core Price Price
56000025 $33.35 $0.00 $23.00
Instrument panel - Instrument panel - Fog lamp switch
Fog lamp switch 1987 - 1989


Part Number Search Results : OEM Catalog

Item Number MSRP Core Price Price
56000025 $33.35 $0.00 $23.00

SWITCH FOG LAMP

 

[JEEPZZ]

JEEPZZ, do you know when just grounding pin #12 if the ECU does the thinking for the rpm raise when in park or neutral, or is there something in the switch that only activates it when in P/N.

No it's not in the switch. When #12 is grounded (via the switch or with a jumper wire directly to the chassis) the PCM recognizes the activation of the extended idle circuit but the PCM also has to have the signal from the NSS telling it that the trans is in neutral or park before it will kick up the idle. (there is no voltage running to pin 12, ground only)

The part numbers for the 97+ ext idle switch and 4 slot bezel are:
4897 505AD 4 switch bezel
5600 8728 extended idle switch
These parts can still be ordered from the dealer. A friend of mine just got one a few months ago.


One last thing: on 4cyl engines pin 12 is a sensor for the steering and NOT a high idle circuit. Only the 4.0L auto trannys have the high idle circuit.

 

[Bryan C.]

I have a pic of the wiring diagram. Not much to say that hasn't already been said. The switch merely completes a path to ground that the PCM recognizes as a request for an idle speed increase. The power feed wire is for the light on the switch.

 

[jxj]

No it's not in the switch. When #12 is grounded (via the switch or with a jumper wire directly to the chassis) the PCM recognizes the activation of the extended idle circuit but the PCM also has to have the signal from the NSS telling it that the trans is in neutral or park before it will kick up the idle. (there is no voltage running to pin 12, ground only)

The part numbers for the 97+ ext idle switch and 4 slot bezel are:
4897 505AD 4 switch bezel
5600 8728 extended idle switch
These parts can still be ordered from the dealer. A friend of mine just got one a few months ago.


One last thing: on 4cyl engines pin 12 is a sensor for the steering and NOT a high idle circuit. Only the 4.0L auto trannys have the high idle circuit.

Jeepzz,
Does the ext. idle switch come with something that plugs into the back of the switch (pigtail wiring). The back of the switch just has the opening and pins, obviously a connector/wiring/relay connects to it (like the fog lamp switch). If the part no. is just for the switch, do you know the part no. for the connector or what did you do to connect the switch to Pin #12. From reading all the post I could find, the back of the switch has four pins #1-z1 20bk Ground, #2 K78 20 gy idle actuator, #3 F15 20db/wt fused ignition switch output #4 E2 20or fused panel lamps dimmer switch signal.
Do you just splice the line (#2-k78 idle actuator) into the grey wire comming out of pin #12 from the back of the PCM (C1)?

 

[5-90]

The PS limit switch isn't a bad idea - but that's only a valid option for four-cylinder XJ's...

None of my RENIX (OK, I'll admit it...) 4.0's have ANYTHING electrical in the power steering circuit - so that's not an option for the rest of us...

I've got to get back to work on this idea - it's been a while, and I've been thinking it for a while myself (although I'm not sure the PSLIMIT request will be high enough - I'd like to see 1200-1500RPM, rather than 1000 or so... I get full alternator output of 180A generated at 1350RPM - if I need it. I'd like to have that available...)

5-90

 

[scoobyxj]

The PS limit switch isn't a bad idea - but that's only a valid option for four-cylinder XJ's...

None of my RENIX (OK, I'll admit it...) 4.0's have ANYTHING electrical in the power steering circuit - so that's not an option for the rest of us...

I've got to get back to work on this idea - it's been a while, and I've been thinking it for a while myself (although I'm not sure the PSLIMIT request will be high enough - I'd like to see 1200-1500RPM, rather than 1000 or so... I get full alternator output of 180A generated at 1350RPM - if I need it. I'd like to have that available...)

5-90

I wonder how hard it would be to trick the ECU into raising the ldle to somthing more like your wanting with the IAC by adjusting the TPS signal. I am think of a potentiometer in series with the TPS's output. It would alow you to adjust your RPM level for the task at hand.

 

[5-90]

Since the IAC is a stepper motor, I've been kicking that around for a while - and someone else is working up a kit (he should have gotten parts for it) that I've offered to test on my rig if he ever gets around to getting it done.

I could see taking over the IAC stepper function, but you'd have to completely disconnect the ECU, and somehow bumfoozle it into thinking that it's still seeing the idle stepper. Then, return IAC control to the ECU and it (should) will automatically return the idle to normal. Since I don't have a test engine stand either (that's a "blue-sky" goal for California, and a definite for Arizona if I haven't done it by then,) I'd have to test it on a "live" rig.

5-90

 

[ghettocruiser]

Hey all... I posted about this awhile back, and got some good brainstorming. As said above, I use this when my York kicks in... right now it raises the idle to around 2000...and since that york pushes tons of air, its only there for a few seconds. Totally adjustable...while not as easy as turning a knob, its really easy to adjust the idel. Gotta do it from under the hood tho. Here isthe post, with our ideas, and what I finally did somewhere on page two with some crappy pics. If anyone wants more info let me know. Been working great for me since i did it with no problems.

http://www.naxja.org/forum/showthread.php?t=64652&page=1&pp=15

Justin

 

[JEEPZZ]

Jeepzz,
Does the ext. idle switch come with something that plugs into the back of the switch (pigtail wiring). The back of the switch just has the opening and pins, obviously a connector/wiring/relay connects to it (like the fog lamp switch). If the part no. is just for the switch, do you know the part no. for the connector or what did you do to connect the switch to Pin #12. From reading all the post I could find, the back of the switch has four pins #1-z1 20bk Ground, #2 K78 20 gy idle actuator, #3 F15 20db/wt fused ignition switch output #4 E2 20or fused panel lamps dimmer switch signal.
Do you just splice the line (#2-k78 idle actuator) into the grey wire comming out of pin #12 from the back of the PCM (C1)?

The switch does not come with any wiring but the connector for the ext idle switch is the same as for the factory fog light switch. I just went to the junkyard and clipped that connector off of a wrecked Jeep. Even XJ's that didn't come with the factory foglights have the wiring connector for the foglight switch plugged into the back of the 'blank' where the fog light switch would go. (btw, plugging a foglight switch into this foglight connector does nothing and the wiring goes no where, but that a whole new can of worms)
So now that you have a ext idle pigtail, just run your own wiring up to pin #12.

 

[hippymill]

I got this info from Tim_MN: thought everyone could benefit from the info, and the parts are fairly cheap if you wanted to put the factory style switch in your XJ.


I might be wrong about the year of the Xj or the parts were just carried over from earlier. The bezel has AMC and the AMC logo on the back side. Bezel P/N 55001893. Ext idle switch P/N is 56000025.
.
They appear to be valid and current P/N's

Item Number MSRP Core Price Price
55001893 $5.35 $0.00 $3.68

HOUSING, SWITCH





Item Number MSRP Core Price Price
56000025 $33.35 $0.00 $23.00
Electrical - Chassis electrical - Switches - Fog lamp switch
FOG LAMP SWITCH, MJ, XJ Series 1992 - 1996


Part Number Search Results : Collision Catalog

Item Number MSRP Core Price Price
56000025 $33.35 $0.00 $23.00
Instrument panel - Instrument panel - Fog lamp switch
Fog lamp switch 1987 - 1989


Part Number Search Results : OEM Catalog

Item Number MSRP Core Price Price
56000025 $33.35 $0.00 $23.00

SWITCH FOG LAMP

 

[JEEPZZ]

I got this info from Tim_MN: thought everyone could benefit from the info,

Repost from page 2.
The part number (listed 3 times) is for a fog light switch not the ext idle switch. The housing number looks right though for pre97.

 

[hippymill]

without looking at the back of the switches i can't be sure, but I'd bet they are the same switch.

 

[scoobyxj]

without looking at the back of the switches i can't be sure, but I'd bet they are the same switch.

Not quite

 

[JEEPZZ]

without looking at the back of the switches i can't be sure, but I'd bet they are the same switch.

OK, I see what your saying; regarding the earlier style switches being the same since the identification marking is on the bezel and not on the switch like the newer style.

The foglight switch is an on/off switch just like the ext idle switch (unlike the momentary rear window defroster switch). :sunshine:

 

[JohnX]

Anyone tried creating a small vacuum leak to increase idle? Could just tee into a vacuum source, run the line inside, and cap it off when not needed?

Any thoughts?

 

[JEEPZZ]

Anyone tried creating a small vacuum leak to increase idle? Could just tee into a vacuum source, run the line inside, and cap it off when not needed?

Any thoughts?

I think that would be the least ideal way to do it.
If someone is looking for a cheaper solution just run a wire off pin 12 and hook it to a generic $1 toggle switch.

 

[JohnX]

I think that would be the least ideal way to do it.
If someone is looking for a cheaper solution just run a wire off pin 12 and hook it to a generic $1 toggle switch.

That's pretty much what I thought, but for someone who doesn't understand wiring, pins, etc. I thought it might be easier for them.

I bet it would raise the idle....but also be very unpredictable, surge, etc.