_Syclone_

I have transplanted a LQ4 6.0 liter out of a 2000 GMC 2500 4x4 into my 1991 GMC Syclone. I have the original wiring harness and computer hooked up that came with the engine. I am using HP Tuners for tuning also. The Engine is hooked up to my 1995-1996 built 4L80E trans. I am not using the original 4L80E trans the engine came with in this build. I do not have it. Anyway, I thought I had everything hooked up correct but the trans is in 2nd gear and will not shift while driving. I guess it is in default mode. I have checked all the wiring from the main connector and the two little ones at the trans and they are all fine. I am missing something little I am sure but can not figure it out. I see in the pin out that there are like 4 other wires at the ECM that are not being used. Labeled like PRND A Input, PRND P Input, TCC Brake switch, PRND B Input. Anyway, I was thinking the 2000 truck it came out of must have another sensor elsewhere I do not have or something like that.

Any ideas?

It will go right into Reverse and drive without a problem. Just will not change gears while driving, stays in 2nd.

Thanks
Will

KySilverado

iTrader: (7)

Do you have the PRND switch on the transmission and wired? I referred to the service manual for a trouble shoot diagram with a second gear only symptom and all it came up with is check the DTC's. Can you do that?

thunder550

iTrader: (70)

You should have a PRNDL switch with 2 connectors on it, the big round connector on the side of the trans, and two VSS sensors.

thunder550

iTrader: (70)

Here's all of the schematics I could find on the 4L80E from a 2000 GMC truck.

Figure 1: Power, Ground, IPC, PCM


Figure 2: CIGAR Fuse, BCM, PCM, DLC, G103, G203


Figure 3: 4L80-E Solenoids, Stoplamp Switch, PCM


Figure 4: 4L80-E Switches, Input Speed Sensor, TFT Sensor


Figure 5: Park/Neutral Switch, Tow/Haul Switch, BCM, G203, G103


Figure 6: VSS Circuit, EBCM, BCM, PCM, IPC

black98ws6ta

iTrader: (75)

The truck does not have the prnd switch hooked up I would assume thats the problem. Does anyone have a pinout for the switch so I can wire it correctly? Earlier it was said that it has two connectors, and I have 4 wires that I know need to go to it from the pcm. I am also assuming that the a/d/b/c at the bottom of the below diagram indicates wire position at the switch in connector c1?






Switch looks like that?

KySilverado

iTrader: (7)

Yes, adbc at bottom are connections at the switch connector. Think the number at the PCM are the PCM pin numbers.

There may be different versions of the switch. I found one on ebay 04 and up that only had one connection.

Here is one for 95 to 03



C1 Connector


C2 Connector

black98ws6ta

iTrader: (75)

WOW, thanks for the help.

There is also a setting in the tune for the PRDNL. NONE (like the f-body), prdnl, or pn only. I think the 4l80's work fine in the f-bodies with just the big round connector, and two vss's, so why wouldnt this one?

KySilverado

iTrader: (7)

Disclaimer here. I'm not certain this is the issue with your trans not shifting out of 2nd but it sure makes sense to me.

As far as it working with a f-body PCM and possibly not with a truck PCM. Different coding in operating systems of the PCM's ??

If you can read the DTC's I suggest doing it. If its squawking with no codes from the neutral safety switch then good chance it is the issue

black98ws6ta

iTrader: (75)

It shows P0758 and P1860.

The truck still has the origional tune in it just switched to 3 bar. Transmission is built and not origionally from the 2000 GMC 2500 truck but it has worked fine before under a tci controller behind the v6 before. It has the 2000 GMC 2500 engine, harness,and pcm in it. I believe he was shorted the two connectors for the switch. He did the swap and I'm finishing it up.

My comment about the f-body was just that I have done a 4l80e before in fbodies and they do not have the pdrnl switch. They just have the round plug, one vss and you have to add the second. Lastly they require a 4l80 segment swap and they work fine. So I was saying it would seem if everything else was hooked up, it would just take flashing this PDRNL option to NONE. That is not working for me though.

thunder550

iTrader: (70)

P0758 = Shift solenoid B Control Circuit
P1860 = Torque Converter Clutch (TCC) Pulse Width Modulation (PWM) Solenoid Control Circuit


Sounds like maybe there's some broken wires in the round connector or something. Neither of those is related to the PRNDL switch.