High Idle with PTO Switch

[3-Fan]

I was looking around on the www.gmupfitters.com site when I stumbled across the high idle publication. It says this:

"HIGH IDLE PROCEDURE FOR C/K 2500HD & 3500 SERIES TRUCKS WITH 6.6L (LB7) DIESEL ENGINE

bulletin zyk 53 11 of 28 2/11/02

High Idle can be obtained by using the 8-pin PTO connector behind the dash and the PTO
accessory kit. The PTO connector can be found behind the passenger air bag defeat switch. It
should be taped to the IP harness directly behind the passenger air bag defeat switch. Mount
the PTO switch next to the passenger air bag defeat switch.

The PTO interface wiring harness included with the PTO Kit is not needed unless
a requirement for remote operation is desired.
Connect the Tech 2 scan tool and reprogram the Engine Control Module (ECM). See the PTO
Programming Guide section for instructions on how to get to the PTO programming screen.
Remember to program to either the Preset PTO or Variable PTO Mode when
using the PTO switch. When the PTO settings are initially read, the settings will
show values of 6000+ rpm. Select the Change Options menu and continue with
the reprogramming of the ECM.
The changes that need to be made are as follows:
PTO Max. Engine Speed 2200 RPM
PTO Standby Speed 800 RPM
PTO Set Speed 1250 RPM
PTO Resume Speed 1700 RPM
PTO Max. Engage Speed 1000 RPM
PTO Shutdown NO
PTO Engage Relay NO
PTO Feedback NO
NOTE:
If the reprogramming of the ECM is not performed, the High Idle function
will not work.

To engage the High Idle, set the Park Brake (manual transmission only) or put the truck in
PARK (automatic transmission only), turn the switch to the ON position. Move the PTO switch
to the SET position or press the SET switch on the cruise control stalk, if equipped. The SET
input ramps up the engine speed to 1250 RPM. By pressing the cruise control, RES/ACC
switch the engine speed will increase to the PTO Resume Speed setting and any SET input will
decrease the engine speed to the PTO Set Speed setting.
If the truck does not have the cruise control option, only the PTO Set Speed is available. The
PTO/High Idle settings can only be changed with a Tech 2 scan tool. The Tech 2 scan tool can
be purchased from GM by calling 1-800-GM-TOOLS.
The PTO accessory kit is available from your local GM dealer.
If any problems should arise, check and clear any DTC's with a Tech 2 and make
sure that the brake switch and tail lamps are functioning correctly.
NOTE:
In certain cases the PTO wiring and connector will not be installed behind the
passenger side air bag switch. If this is the case, the system will need to be hardwired
into the ECM and a switch or switches (no cruise control) will need to be
used. Please call the Upfitter Integration Hotline at 1-800-875-4742 for more
information."

It says nothing about running a wire to the ECM. I have a PTO switch but no Tech 2. I was curious if anyone out there had tried this with the PTO switch and a Tech 2 and if it works. I'd be willing to send someone my PTO switch to try this out if they have a Tech 2. I know a few of you guys have played around with the Tech 2 and the high idle, but I think that was with high idle hard wired to the ECM.

[mdrag]

3-Fan,

"It says nothing about running a wire to the ECM."

The last paragraph of your post:

"NOTE:...the system will need to be hardwired
into the ECM and a switch or switches..."

My '01 crew cab did NOT have the PTO connector as described in your post (or I can't find it), so it was necessary to run the wire, add a terminal to the ECM, and add a switch as described in previous posts on this topic.

I don't remember anyone posting using the PTO wiring/harness for the high idle, but it would make it easier.

[SUNBUM32]

HELP !! Dose anyone know where the 8 pin wires behind the dash end up under the hood?? I have the wirring behind the dash and am hopping to find out where they end up under the hood so I can run one of the existing wires to the ECM and the other end to the switch. I wish I had a shop manual now. Thanks for your Help.

[AKDmax]

I was talking to Maverick about the wiring harness also. When you looked up the PTO information did you take note that it was for the chassis cab pickups? Don't think the non chassis cab P.U.'s have the wiring harness in them because they are not setup for PTO like the chassis cabs are. It's too easy to run the wire to the ECM, why bother with the PTO harness?

[3-Fan]

mdrag,
"The last paragraph of your post:

"NOTE:...the system will need to be hardwired
into the ECM and a switch or switches...""

My take on that was you had to hardwire it only if you didn't have cruise. Or some other case like yours.

AKDmax,
There is more to the publication than what I pasted in. Instructions for high idle for 3500HD, 3600C/K Chassis Cab and also all the above with the 8.1L also. Then instructions I pasted said for 2500HD and 3500. They also list a fast idle for the 8.1L only.

My 2002 has the 8 pin connector that plugs right into the back of the PTO switch. It is wire tied back behind the passanger side airbag to itself. Had to shove my arm in up to my elbow to find it. When I plugged my PTO switch into it, nothing happened in park. But while on the road, the switch acts just like the cruise stick. It says it won't work unless you reprogram with a Tech 2

I know it isn't hard to wire it right to the ECM. Mine is already done. But was just trying to look out for some others that don't want to attempt to tap into the ECM themselves. I know I was a little nervous doing it. Plus for the $40 for the PTO switch isn't too bad considering what you don't have to do then. You just need to find someone with a Tech 2.

[Carli_max]

3-Fan,

What does the PTO switch look like, and where can you mount it?? I have a 2500 CC and there is no passenger air bag switch. Also, I cut & pasted the URL for the Upfitters, and it errors. Could you check it and re-post it? I haven't added the High Idle, cause I didn't like the idea of playing with the ECM. This sounds like an easier way!!

[3-Fan]

Carli_max,

Sorry on the link. Try this:

https://www.gmupfitter.com/secure/html/

Goto the publications tab and then the technical bullitens tab. You should then see the "#53 Power Take Off (PTO) & High Idle" article.

The PTO switch is the same size at the airbag switch (1.5" x 1.5" or so), has a circular knob on it and says on, off, and set on it. It has a back light and a couple of LED lights that come on when it is on.

The part number for this per the article is:

#12497678 it is listed $31.50 on GMpartsdirect.com

SInce you don't have the airbag switch, you might need to order the housing and blank covers that hold the PTO switch and the airbag switch.

Those part numbers are:

# 15040484 - 4 Pod Housing
# 15040483 - 2 Pod Housing
# 15734687 - Blank Cover Plates (5 per pack)

Like I said, I don't know if this works the way the article says. I was hoping someone with access to a Tech 2 would try it out for us.

[dmaxster]

I have the PTO sw...installed in mine and it doesnt' work any different than the way all the other guys have thiers wired.....I had thought it would but it doesn't.....so the long and short of it is that the way all of us who have this already works and is alot cheaper....anyways the only thing that I have noticed is that the PTO sw acts the same as the cruise...no different....set is set and that is it....it doesn't increase the RPM's differently you still need to use the cuise stick....if you would have any more questions feel free to email me madenterprises@itol.com .... I had thought this would be alot nicer than some ol switch but you still need the sw and to run the wires to the ECM the same as we have been....this is what I all learned and picked up as I had spent the money...If someone else know's something different let us all know....Thanks Dave

[keilb]

On my 03 GMC D/A 2500, found the plug and installed the PTO switch. My friendly local service manager and I reprogrammed the ECM with the TechII as per the instructions on the upfitter bulletin #53. No luck! The switch works as cruise control but no high idle. Has anyone done this successfully?

[SUNBUM32]

I think I have read here before that you need to add a plug in harness under the hood that plugs in to the ECM before the PTO switch will work?? I am trying to find out were the 8 pin conector ends under the hood, dose anyone know?? Thanks!