Anyone have access to ALLDATA or the like? (GMC Jimmy PCM Pinouts -tow/haul)

[andy396]

I’ve been poking around in my 2000 “black box” PCM tune using HPTuners and noticed it has a second shift table. After much googling the only thing I can come up with is a rumor that the GMC Jimmy in the ‘98-00 era with a 4.3L had an optional tow/haul mode. One statement eluded to that it might be activated by pin 12 on the blue C1 connector, which is just listed as “empty” for my PCM pinout. From what I can tell, the Jimmy didn’t get the ‘0411 PCM until maybe 2001 or 2002 and so it would seem to have a tow/haul mode using a black box pcm. I was wondering if anyone who has access to the pinouts of other vehicles might be willing to look into this for me?

There’s even a switch on eBay that claims to be from a ‘99-01.

https://www.ebay.com/itm/NEW-OEM-GM...720923?hash=item1ee3f8525b:g:UO0AAOSwTfdbLR3a

 

[b454rat]

Dunno why trucks did the have it. Haven’t heard of S-10s having it but have in Astro’s...be interesting to find out, be nice feature to have.

 

[Jglew82]

From what I can tell, the Tow/Haul button sends a signal to the BCM which then sends a class 2 serial data signal to the PCM via C4 pin 14, yellow wire (based on an Astro diagram) which may be empty on yours. I know there's an option on the 0411's and P59 to change this to a simple ground signal in the tune, but you'd need to verify that for the black box.

 

[andy396]

From what I can tell, the Tow/Haul button sends a signal to the BCM which then sends a class 2 serial data signal to the PCM via C4 pin 14, yellow wire (based on an Astro diagram) which may be empty on yours. I know there's an option on the 0411's and P59 to change this to a simple ground signal in the tune, but you'd need to verify that for the black box.

C4 pin 14 is “not used” on my black box. What would your suggestion be, test this pin for voltage and if there’s voltage, send a momentary ground to this pin and see if it switches to the values in that other table via a test drive?

 

[Jglew82]

First off, in HPtuners, do you have the following options? Transmission tab>General>Perf Option>(dropdown list)? If so, chose the setting in the list to "one switch."

 

[andy396]

Edit: No, the only thing in the trans>shift general tab is Force Motor Current

 

[andy396]

The one switch, two switch, class 2 option seems to be a 0411 PCM only thing. The black box alternate shift table is labeled as “economy”.

 

[Jglew82]

Interesting. I haven't messed with the black boxes very much, so I'd be hesitant to advise you on trying to ground the terminal to test, but I don't see any harm in testing to see if that terminal is resting at voltage.

Maybe someone else can chime in, or hop on the HPTuners forum and try asking there? They'll probably just tell you to 0411 swap it, lol.

 

[andy396]

The threads I could find on the topic all either dead ended or said just swap it to a 0411. If I could get this second shift table active this ‘00 black box seems to have every adjustment I would want to play with.

Did you try looking at a ‘99-00 Jimmy/Blazer diagram and pinout?

 

[Jglew82]

Yes, Blazer/Jimmy are the same as the astro - C4 pin 14 yellow from BCM.

2001 was when they went to the 0411.