L92 6L80E Swap - Trans in limp mode - DTC P2534
08-25-2011, 07:29 PM
#1
L92 6L80E Swap - Trans in limp mode - DTC P2534 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.
Help!
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.
Help!
08-26-2011, 08:25 AM
#4
I had an epiphany.
I think the DTC may be setting at key OFF timing.
When you turn the key off, the ECM does not immediately shut off.
But due to being wired directly to the ignition, the TCM may shutdown.
Since the ECU is still powered and on, the TCM sets a code.
So wiring a TCM relay to be controlled by the ECU, should fix the problem.
When the ECU is on, the TCM is on.
I think the DTC may be setting at key OFF timing.
When you turn the key off, the ECM does not immediately shut off.
But due to being wired directly to the ignition, the TCM may shutdown.
Since the ECU is still powered and on, the TCM sets a code.
So wiring a TCM relay to be controlled by the ECU, should fix the problem.
When the ECU is on, the TCM is on.
08-26-2011, 10:05 AM
#5
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I have the same problem with my ly6 6l90. I just clear the code everytime I start the car. I came to the same conclusion about adding a separate relay for the tcm after contacting the guy who posted the problem on efilive forum. I am using the bcm but it shouldn't be any different.
How does your trans act in limp home mode? Mine makes a weird grinding noise.
How does your trans act in limp home mode? Mine makes a weird grinding noise.
08-26-2011, 02:07 PM
#6
I have the same problem with my ly6 6l90. I just clear the code everytime I start the car. I came to the same conclusion about adding a separate relay for the tcm after contacting the guy who posted the problem on efilive forum. I am using the bcm but it shouldn't be any different.
How does your trans act in limp home mode? Mine makes a weird grinding noise.
How does your trans act in limp home mode? Mine makes a weird grinding noise.
08-26-2011, 08:52 PM
#7
TECH Resident
I had an epiphany.
I think the DTC may be setting at key OFF timing.
When you turn the key off, the ECM does not immediately shut off.
But due to being wired directly to the ignition, the TCM may shutdown.
Since the ECU is still powered and on, the TCM sets a code.
So wiring a TCM relay to be controlled by the ECU, should fix the problem.
When the ECU is on, the TCM is on.
I think the DTC may be setting at key OFF timing.
When you turn the key off, the ECM does not immediately shut off.
But due to being wired directly to the ignition, the TCM may shutdown.
Since the ECU is still powered and on, the TCM sets a code.
So wiring a TCM relay to be controlled by the ECU, should fix the problem.
When the ECU is on, the TCM is on.
The D2534 DTC is set to indicate that the voltage on the run-start line is below 6V for 2 or 3 seconds after the engine is started.
The ECM and TCM must have both the full time 12V and the run-start key on 12V. Limp mode occurs for a number of reasons beyond the power sup voltages like incorrect trans tune, no trans tune (happens a lot with new never run factory transs), faulty CAN connection, badly installed shift selector switch etc.
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08-26-2011, 09:50 PM
#8
When the ECM and the TCM see the power removed from the key on/run-start supply line the maintain an on-state using the full time power. They do this so they can shut down in an orderly manner and save any learned parameters (i.e. fuel trims) to long term memory. Normally around 10-15 seconds.
The D2534 DTC is set to indicate that the voltage on the run-start line is below 6V for 2 or 3 seconds after the engine is started.
The ECM and TCM must have both the full time 12V and the run-start key on 12V. Limp mode occurs for a number of reasons beyond the power sup voltages like incorrect trans tune, no trans tune (happens a lot with new never run factory transs), faulty CAN connection, badly installed shift selector switch etc.
The D2534 DTC is set to indicate that the voltage on the run-start line is below 6V for 2 or 3 seconds after the engine is started.
The ECM and TCM must have both the full time 12V and the run-start key on 12V. Limp mode occurs for a number of reasons beyond the power sup voltages like incorrect trans tune, no trans tune (happens a lot with new never run factory transs), faulty CAN connection, badly installed shift selector switch etc.
The issue here is a nuance of the GM engine/tran combo in a swap platform.
I guess I didn't understand if you're just relaying basic information(which I do appreciate) or trying to share an opinion/idea on what's actually wrong. No offense.
Anyway, I plan to tie my TCM relay into a ECM controlled source tomorrow morning. I'll post here if thats the fix. This is one of those things that should be in the sticky information for conversions.
Thanks
08-27-2011, 01:44 AM
#9
TECH Resident
I guess I didn't understand if you're just relaying basic information(which I do appreciate) or trying to share an opinion/idea on what's actually wrong. No offense.
Anyway, I plan to tie my TCM relay into a ECM controlled source tomorrow morning. I'll post here if thats the fix. This is one of those things that should be in the sticky information for conversions.
Thanks
Anyway, I plan to tie my TCM relay into a ECM controlled source tomorrow morning. I'll post here if thats the fix. This is one of those things that should be in the sticky information for conversions.
Thanks
A regular production car feeds the ECM and TCM key on power from the same run/crank relay so they both get power at the same instant. You will hear the TCM stay on after the key on power is removed too. Squeals like a stuck pig (a mile away).
If adding in a relay fixes the limp mode problem that is a wierd one
.
08-27-2011, 09:20 AM
#10
Fair enough. No problemo. Its not an opinion, its 3 years worth of experience exactly these type of swaps and running the ECM and TCM on the same run/start power source from the key with no relays.
A regular production car feeds the ECM and TCM key on power from the same run/crank relay so they both get power at the same instant. You will hear the TCM stay on after the key on power is removed too. Squeals like a stuck pig (a mile away).
If adding in a relay fixes the limp mode problem that is a wierd one.
A regular production car feeds the ECM and TCM key on power from the same run/crank relay so they both get power at the same instant. You will hear the TCM stay on after the key on power is removed too. Squeals like a stuck pig (a mile away).
If adding in a relay fixes the limp mode problem that is a wierd one
.Its only happens at startup or shutdown. I originally had it wired to
the same fused ignition source. Now I have separated that to remove it as a variable. But they still are current both powered simultaneously powered at key on. I've monitored the ignition voltage at key on and it stays a steady 12V between run-start-run.
I need ideas.
Something else I did think of. There are two sets of CAN lines that go to the trans. One sets goes back to the ECM. The other must have gone to the BCM. I currently have those unconnected. Could that be a cause? No BCM? Why wouldn't it code all the time, not just startup. Furthermore it doesnt fit with the definition of the code.
08-27-2011, 10:18 AM
#11
TECH Resident
Okay, well then what do think the problem is? On your swaps do you use the BCM? Have you done a L92/6L80E?
Its only happens at startup or shutdown. I originally had it wired to
the same fused ignition source. Now I have separated that to remove it as a variable. But they still are current both powered simultaneously powered at key on. I've monitored the ignition voltage at key on and it stays a steady 12V between run-start-run.
I need ideas.
Something else I did think of. There are two sets of CAN lines that go to the trans. One sets goes back to the ECM. The other must have gone to the BCM. I currently have those unconnected. Could that be a cause? No BCM? Why wouldn't it code all the time, not just startup. Furthermore it doesnt fit with the definition of the code.
Its only happens at startup or shutdown. I originally had it wired to
the same fused ignition source. Now I have separated that to remove it as a variable. But they still are current both powered simultaneously powered at key on. I've monitored the ignition voltage at key on and it stays a steady 12V between run-start-run.
I need ideas.
Something else I did think of. There are two sets of CAN lines that go to the trans. One sets goes back to the ECM. The other must have gone to the BCM. I currently have those unconnected. Could that be a cause? No BCM? Why wouldn't it code all the time, not just startup. Furthermore it doesnt fit with the definition of the code.
Your CAN lines should really have a 120 ohm resistor across the end if they are still wired like that, certainly probably CAN errors if not. Where is your diagnostic connector? BCM is not required.
Assume you have had a good look at the pins in the trans end connector. These have a record with GM on some models of not being tight in and get noisy. Checked for 12V on the two power pins?
08-27-2011, 10:34 AM
#12
Different engines and A6's but this is about E38/E67 and T43. What ECM and TCM tune are you running?
Your CAN lines should really have a 120 ohm resistor across the end if they are still wired like that, certainly probably CAN errors if not. Where is your diagnostic connector? BCM is not required.
Assume you have had a good look at the pins in the trans end connector. These have a record with GM on some models of not being tight in and get noisy. Checked for 12V on the two power pins?
Your CAN lines should really have a 120 ohm resistor across the end if they are still wired like that, certainly probably CAN errors if not. Where is your diagnostic connector? BCM is not required.
Assume you have had a good look at the pins in the trans end connector. These have a record with GM on some models of not being tight in and get noisy. Checked for 12V on the two power pins?
I have no CAN DTC's. The open can lines are for the body control module. The lack of the 120 Ohm resistor should cause a "BCM Not Found" type code right? I'm not getting one. But its a good idea. I'll try to track down where they end and find a resistor.
I have checked for power on the TCM pins. If the connection was noisy, why would the trans not go into limp mode going down the road?
Problem only happens at the key cycle, a loose pin shouldn't wait until the key cycle.
08-27-2011, 03:50 PM
#14
Well, it seems to be fixed. I rewired my TCM relay to be power by the main relay(ECU controlled), and no more P2534 code. No I can more clearly hear the trans staying on after key off.
I let you know if for some reason it comes back. But I drove it and cycle the ignition enough times to where it would have normally reoccured.
I let you know if for some reason it comes back. But I drove it and cycle the ignition enough times to where it would have normally reoccured.
08-27-2011, 10:01 PM
#15
TECH Resident
Well, it seems to be fixed. I rewired my TCM relay to be power by the main relay(ECU controlled), and no more P2534 code. No I can more clearly hear the trans staying on after key off.
I let you know if for some reason it comes back. But I drove it and cycle the ignition enough times to where it would have normally reoccured.
I let you know if for some reason it comes back. But I drove it and cycle the ignition enough times to where it would have normally reoccured.
. the internal TCM is calle a T43.
09-08-2011, 08:59 PM
#16
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RSZ288, my wiring is almost identical to stock but yet i am having this problem. It doesnt make sense but i will be adding a separate trans relay when i get a chance.
09-10-2011, 12:09 AM
#17
TECH Resident
09-10-2011, 02:16 PM
#18
yeah, bsharpe, what is stock?
The diagram I saw for a stock Escalade 6L80E shows a relay controlled by the body control module. If you're not running the BCM(I am not), then its not stock.
Anyway, my new relay setup is working fine for me.
The diagram I saw for a stock Escalade 6L80E shows a relay controlled by the body control module. If you're not running the BCM(I am not), then its not stock.
Anyway, my new relay setup is working fine for me.
09-10-2011, 09:21 PM
#19
TECH Resident
09-10-2011, 10:58 PM
#20
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Both the TCM and ECM are powered by the same relay which is triggered by the BCM. illustrated by the links below.
http://repairguide.autozone.com/znet...3f807dc8ee.gif
http://repairguide.autozone.com/znet...3f807dbf1d.gif
I am using the bcm to trigger the relay but i dont think that makes a difference. Either way I dont see a reason to use a separate relay.
Did you use the yellow/black wire pin 52 to trigger your tcm relay? . Take a look at http://forum.efilive.com/showthread....le-guide/page3this thread which discusses the problems with the starter relay wire. I used hptuners to disable the starter checks and figured that handled that problem.
I still dont see how this is connected to the tcm power issue but it makes more sense then needing a separate relay.
http://repairguide.autozone.com/znet...3f807dc8ee.gif
http://repairguide.autozone.com/znet...3f807dbf1d.gif
I am using the bcm to trigger the relay but i dont think that makes a difference. Either way I dont see a reason to use a separate relay.
Did you use the yellow/black wire pin 52 to trigger your tcm relay? . Take a look at http://forum.efilive.com/showthread....le-guide/page3this thread which discusses the problems with the starter relay wire. I used hptuners to disable the starter checks and figured that handled that problem.
I still dont see how this is connected to the tcm power issue but it makes more sense then needing a separate relay.
