High Idle question

[drgracr]

I have a question about high idle
I have a 08/01 production 2002 and I read that there might be a pto connector inside the dash area. If is does exist where might I find it.

thanks

[SteveO]

drgracr,

If your truck was a 3600 series, That's a 3500 Chassis Cab >>no bed and normally has straight frame rails then the truck could have been ordered with the PTO Option which includes, Wiring Harness> Operation wiring/connector is behind the cubby hole. The other part of the Harness is on top of the transmission to plug the PTO into and the last thing is a BIG bulge in the Passenger side floor board so the PTO can be bolted to the trans.. The bulge is removable to gain access to the top mounting bolts of the PTO...

Sorry..

[ 01-15-2003: Message edited by: SteveO ]</p>

[mdrag]

SteveO and drgracr,

I reviewed a document from GM Upfitters (UI Bulletin #53) on the subject of the PTO and High Idle. These can be a bit confusing to say the least...Here is a quote from that document:

SUBJECT: Power Take Off (PTO) & High Idle
MODELS AFFECTED: C/K 3600 Cab Chassis,
3500, 2500 HD and 3500 HD with the 8.1L
(L18) Gas & 6.6L (LB7) Diesel Engine
MODEL YEAR(S): 2001 and Beyond
DATE: 2/11/02

"Wiring provisions for in-cab PTO Control switch is provided in most of the
Light Duty trucks with the 8.1L (L18) gas or 6.6L (LB7) diesel engines only."

The 8-pin PTO connector is described as being located behind the airbag disable switch.

That being said, I didn't see the connector behind the cubby when installing my SPA gauge(there is no airbag disable switch on crew cabs), and have yet to come across it in my truck, a late '01.

I remember at least one forum member finding such a connector, and obtaining the GM PTO switch for the dash. He found that the PTO switch worked like cruise control and did NOT provide the high idle function.

[3-Fan]

I bought the PTO switch and found the 8 pin connector behind the airbag switch. It was hard to find. I seemed like I had to shove my arm in up past my elbow to find it. It was zip tied back to itself. Plugged the switch in and no high idle that's for sure. Acted just like the cruise stick.

But as the Upfitters article says, certain parameters in the ECM (for 6.6L and PCM for 8.1L) need to be set for this to work. And I don't have access to a Tech 2 to set these parameters. Maybe somebody that has a Tech 2 could check this out. I'd be glad to send my PTO switch to them to test it.

[mdrag]

3-Fan,

Did you end up installing the high idle using a non-PTO switch? It would be interesting to know if the light green wire at ECM position C1-71 was factory installed? Or is the other end of that PTO harness connected or just taped up somewhere :confused: ...

[3-Fan]

mdrag,

I used the PTO switch as my SPST switch to get juice to the ECM. I was able to stuble across the right 8 pin connector (the same as is on the PTO harness tucked behind the air bag switch) that connected into the back of the PTO switch. I was able to probe the guts of the PTO switch to find what the different switch positions would activate which pins on the back. All's that I have wired in is the power in, ground, and out to the ECM Pin that I installed. It has a back light when the lights are on and then when the switch is in the on position it has an amber light that blinks. Kinda cool looking.

I don't understand the Upfitters article. By their report, it sounds like all the wiring is factory installed to have this new PTO switch communicate with the ECM. Just some reprogramming with a Tech 2. So the wire we run to the ECM is not required. I Have heard that the Chassis cabs you can order with the PTO switch factiry installed. You would think that GM would use the same harnesses in all their trucks. So if it is there for the Chassis cab, why wouldn't all the right wiring be there in the 3500 and the 2500HD's?

You lost me on the light green wire?

[johnpugh]

Actually, I'm about to start the high idle install on my truck. I have already found the connector ing the dash and I already have the GM switch kit (PN 12497678).

Just for the heck of it, I called the GM Upfitters hotline and the guy on the other end confirmed that the 2500HD/3500 engine harness does not include the necessary wiring to the ECM. The IP harness is the same for our trucks as well as the 3600. I have the schematic and according to it (and the tech guy), the wire for circuit 488 (PTO Enable) stops at connector C106.

So it looks like I have two options, cut the PTO enable wire (Circuit 488) close to the switch connector and run wire from there to the ECM or find connector C106 and extend a wire to the ECM from there.

I'd prefer to find Connector C106, but I haven't had much luck (not really searching, just looking around). Does anyone know exactly where connector C106 is located???

[drgracr]

Thanks guys, looks like I'll be stringing more wire to the ecm. No fun involved there.

[mdrag]

JMPDMax,

C106 is a 6 postion connector. Looking at the terminal end view with the connector release on top, pin A is on the right and pin F is on the left. This is for the FEMALE side of the connector.

15326829
6-Way 150 Sealed (BLK) FEMALE

Pin Wire Color Circuit No. Function
A YEL 2522 Power Take Off (PTO) Feedback Signal
B GRY 48 CPP Switch Signal
C LT GRN 488 Power Take Off (PTO) Enable Signal
D YEL 2470 ECM/PCM Class 2 Serial Data (Allison Transmission)
E DK BLU 84 Cruise Control Set/Coast Switch Signal
F PPL 420 TCC Brake Switch Signal

Where is C106? I could not find it in the 2001 Helm manual - no desciption or diagram. I found C105, C107, and C108. C105 is described as "At the left side of the engine compartment near the Junction Block - Underhood" From the diagram, C105 appears to be on the passenger side somewhere near the hydroboost assembly . C107 (38 pin) and C108 (24 pin) appear to be the two large connectors on the pass side of the engine, with the locking levers, on top and very visible.

C106 should be somewhere close to these there - I'll have a look...

3-Fan,

Light green is the OEM color of the wire for circuit 488, PTO Enable Signal. I was trying to determine if trucks with the factory PTO connector had a light green wire already in place at ECM position C1-71. JMPDMax seems to have answered my question - no, not factory connected.

mdrag

[johnpugh]

Hey mdrag:

Did you ever find connector C106?

[mdrag]

JMPDMax,

I was not successful in finding connector C106 on my truck. I poked around for a good 15 minutes or so...and had a strange feeling that I had tried this exercise before :eek:

There are few connectors UNDER or within the underhood junction block...I did not take it apart to look however...that location is a prime suspect at this point...

I vaguely think I remember...maybe...that there is a connector on the leading edge of the junction block when you take off the top, release the tabs on the engine side, and pull the entire plastic assembly upward :confused:

mdrag