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Could really use help, what wire from PCM did you use and what wire to the TCM did you use
Originally Posted by BelAir1000
Hey guys,
Recently finished the swap on my '68 Bel Air Wagon.
I have a 07 Escalade L92 and 6L80E.
The problem I'm having is the trans will generally go into limp mode
when I cycle the key to ON. The DTC 2534 sets when this happens.
DTC P2534 is Ignition Switch Run Start Circuit Low.
I made my own harness. Everything else works great.
For power to the trans, I started off with a single wire and 20 amp fuse from my ignition switch(OE fuse box) and then splitting to power both the ECM and TCM.
When I clear the DTC's, I have normal trans function on all 6 gears. As soon as I cycle off and then On the dtc resets and I am back to limp mode.
So it makes me think two things are happening, either the trans doesn't get enough power at key on or the TCM get power too soon and needs to be sequenced...i.e. get power only after the ECM is booted up.
Today I set up a relay(power by the previous ignition switch circuit) and 20a fuse and getting power from the "Battery" terminal on my fuse box. I am getting constant power to the trans as far as I can tell so I don't think its a power issue.
I did also see a post on another forum from another guy that was getting the same code. He rewired his to get power by a relay controlled by the ecu for both pin 12 and 6. Pin 6 is the Accessory Serial Data?
Do I need to power the serial data pin 6? That seems weird to me.
So next up I will try to sequence the power on and see if that matters.
I have these directions from my harness builder about this very issue. Problem has been solved since 12 to 15 months without a single glitch, since.
pin (on connector C1 #59) supplies the ground which will energize the relay coil being added to the system to power the TCM. I had to add the pin to the connector where initially it was blanked out.
Last edited by DW SD; 11-20-2015 at 06:36 PM.
Reason: I should have written TCM, not ECM.
To add to what I just wrote... There is a pink power wire, I believe, in the transmission connector. The output from the relay powers that pink wire. I need to find a schematic to confirm.
That schematic, I bet, is in one of the links provided earlier in the thread.
Oh yes, here it is on this schematic. The wire is labeled PK. Pink. In summary wire: Ground trigger to the relay coil (85) is pin 59 on connector C1. Wire battery 12V+ to the other side of the relay coil (86) and to the relay power feed (30). Output (87) to the pink wire on the transmission bundle.
Looks like Pin 12 on the transmission connector in Pink.
Hi Tony,
I just reread as its been 4+ years.
Follow the instructions in post 24. Mine's been working fine for 11k miles and 4 years.
Let the ECM turn on and off power to the TCM via the added relay.
Hi Tony,
I just reread as its been 4+ years.
Follow the instructions in post 24. Mine's been working fine for 11k miles and 4 years.
Let the ECM turn on and off power to the TCM via the added relay.
Tony,
Let us know you get this worked out.
These are the instructions I provided offline for someone in the future, which is probably redundant.In my case, my harness builder sent me a length of wire and a compatible pin to add to ECM connector C1 (I think). I removed the connector and pushed that pin in to the harness in the right slot. I think pin 12 had a wire already. And I cut that and connected the output of the new relay (87) to power the TCM. I might have it backwards in terms of which pin I added to which connector, but am 80% sure that is right.
To recap. output ECM C1 pin 59 to new relay pin 85. fused, 12V+ (not switched) to relay pins 86 and 30. Relay pin 87 to transmission harness pin 12 (pink wire).
Cheers,
Doug
11-20-2015, 04:54 PM
