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P150C-00, U0101, C0055, C0201

Odlaw

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Hey Guys, been many moons since I've posted anything on TTS. That is mainly because my d-max has been trouble free for 250k miles now. Anyway, was 6 miles in after cold start and cruise kicked off, speedo stopped working and just about every light on the dash came on and the gear shift indicator light went out. The dic showed SERVICE BRAKE SYSTEM with ABS and BRAKE light on. I was cruising at 60 mph. Once I pulled over tranny was in limp mode stuck in 2nd gear and would not upshift or downshift. I limped it back to my house and started trouble shooting. First, I removed the grounds (behind left front bumper and under driver door) and cleaned them even though they looked good. ohm'd out B3 on EBCM to C2-pin 54 on ECM, solid connection. Tested to ground for a short, open. Checked every connector I could find. Checked rear wheel speed sensor (ohm'd around 1.4 or 1400 milliohms) and output shaft for play, may have had a 32'nds of play...barely any. Speed sensor looked good and no evidence of contact with the reluctor wheel (or whatever the 6 speed ally has). Took it for another test drive and about 6 miles later same thing. The codes I listed above in the title are in reverse order, left - right, most recent to first code. Was still getting C0055 along with the latest P150-C-00. So I picked up a new rear wheel speed sensor even though I knew it was not going to fix the issue. Replaced the speed sensor. Now it throws codes (C0055 and U0101-lost comm with TCM) as soon as I moved about 5 feet out of my shop. It occasionally (like it did just now) goes into what feels like the allison quick learn procedure that will give you serious pucker factor as the ally just slams into different gears, mostly on it' own...violent shifts. When I clear those two codes, the SERVICE BRAKE SYSTEM message literally comes back before my scanner displays "codes cleared successfully". I'm using my old HF Zurich ZR8 that will read and clear ABS codes. It's starting to look like the TCM but I prefer not to throw money at the problem until I know it will fix it. The the moderators, feel free to move this if needed. I just took the highest percentage of codes (tranny related) and stuck this in the tranny section.
Any help would be greatly appreciated.
Thanks guys
Smitty
 

btfarm

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Sounds to me like TCM as well but the brake system code is making me think different. You might get a better answer from @THEFERMANATOR as he's very knowledgeable about these Allisons
 

Rockabillyrat

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Here are the test procedures for the issues your having. TCM issues are not uncommon with thoes.


1. Verify battery voltage is present at the "ACCY, On and Start positions of the ignition switch on the Pink wire at pin 63.

2. Verify battery voltage all the time at the Orange wires at pins 10 and 70.

3. Verify a good ground on the Black/White wires at pins 9 and 69.

4. If OK, check the resistance between pin 6 and pin 14 of the DLC with the key OFF. It should be 60 ohms +/- 10%.

5. If OK, replace the TCM. Programming is required after installation.


Also gm issued a few TSB help diagnose this issue. Here they are...

Condition/Concern:
Vehicles equipped with the Allison LCT1000 Automatic Transmission may exhibit one or more of the following conditions:

DTCs P0721, C0237, P0500, C0055

Speedometer inoperative, erratic or drops out

Cruise control inoperative

Radio speed control volume (SCV) inoperative

Transmission shifting concerns

ABS light illuminated

The following diagnostic approach may be helpful in repairing any of the above conditions.

The testing should begin at the VSS sensor located in the rear of the transmission on 2WD models and in the transfer case on the 4WD models. An erratic signal caused by a loose or damaged reluctor wheel can cause any of the above concerns.

Recommendation/Instructions:
On vehicles equipped with the Allison LCT1000 Automatic Transmission, the VSS signal is sent to the Transmission Control Module (TCM) via Circuits 821 and 822.

The signal from the VSS to the TCM is an A/C signal that produces approximately 28-34 HZ per 1 mile per hour. This signal can be checked using a Fluke 87 (DVM) set on the A/C voltage scale with hertz function activated and connecting leads to Circuit 821 and 822.

The TCM converts the VSS signal from an A/C sign wave to a digital wave. The TCM sends out approximately 4.5 volts on Circuit 400 to the PCM/ECM. With the vehicle stopped, the DVM will read approximately 4.5 volts on circuit 400, but once the vehicle begins to move the voltage will drop to near 0 volts. To check the voltage with the DVM with the vehicle moving, the min/max function should be set to 1 ms, the max should be 4.5 volt and the minimum should be -4.5 volts. The reason the reading goes negative is because the TCM converts the A/C signal from the VSS to the exact digital wave, therefore when checking the HZ signal on circuit 400 the fluke meter can be set on the A/C or D/C signal with hertz mode active. Circuit 400 can be checked by backing out the terminal at the ECM/PCM connector and placing the red lead of the meter to Circuit 400 and the black lead to ground. The signal from the TCM on circuit 400 will be the same HZ reading as the VSS approximately 28-34 HZ per 1 mile per hour.

The vehicle speed signal to the IPC, radio, cruise control module, and body control is provide by the ECM/PCM on Circuit 817


The second one


Condition/Concern:
ABS light on speedometer may be erratic. DTC C0055 C0235 C0236 or C0237 stored in the EBCM. This concern may be intermittent and not easily reproduced.

Recommendation/Instructions:
Using the Tech 2, check the ECM/ PCM and/or TCM for any speed sensor or communication related DTCs. These DTCs will need to be diagnosed first. Follow published diagnostics for related DTCs and evaluate the vehicle after repairs are complete. If no DTCs exist in any other module, inspect the rear VSS sensor circuit(s) from the rear VSS sensor to the related module (ECM, PCM or TCM) for integrity. These circuits are 821 and 822 or 400 and 401 depending on model and model year (use SI to locate the schematic that applies to your application). Repair or restring these two circuits as needed. Evaluate the vehicle.
 

btfarm

America First!
Staff member
Lead Moderator
Messages
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Here are the test procedures for the issues your having. TCM issues are not uncommon with thoes.


1. Verify battery voltage is present at the "ACCY, On and Start positions of the ignition switch on the Pink wire at pin 63.

2. Verify battery voltage all the time at the Orange wires at pins 10 and 70.

3. Verify a good ground on the Black/White wires at pins 9 and 69.

4. If OK, check the resistance between pin 6 and pin 14 of the DLC with the key OFF. It should be 60 ohms +/- 10%.

5. If OK, replace the TCM. Programming is required after installation.


Also gm issued a few TSB help diagnose this issue. Here they are...

Condition/Concern:
Vehicles equipped with the Allison LCT1000 Automatic Transmission may exhibit one or more of the following conditions:

DTCs P0721, C0237, P0500, C0055

Speedometer inoperative, erratic or drops out

Cruise control inoperative

Radio speed control volume (SCV) inoperative

Transmission shifting concerns

ABS light illuminated

The following diagnostic approach may be helpful in repairing any of the above conditions.

The testing should begin at the VSS sensor located in the rear of the transmission on 2WD models and in the transfer case on the 4WD models. An erratic signal caused by a loose or damaged reluctor wheel can cause any of the above concerns.

Recommendation/Instructions:
On vehicles equipped with the Allison LCT1000 Automatic Transmission, the VSS signal is sent to the Transmission Control Module (TCM) via Circuits 821 and 822.

The signal from the VSS to the TCM is an A/C signal that produces approximately 28-34 HZ per 1 mile per hour. This signal can be checked using a Fluke 87 (DVM) set on the A/C voltage scale with hertz function activated and connecting leads to Circuit 821 and 822.

The TCM converts the VSS signal from an A/C sign wave to a digital wave. The TCM sends out approximately 4.5 volts on Circuit 400 to the PCM/ECM. With the vehicle stopped, the DVM will read approximately 4.5 volts on circuit 400, but once the vehicle begins to move the voltage will drop to near 0 volts. To check the voltage with the DVM with the vehicle moving, the min/max function should be set to 1 ms, the max should be 4.5 volt and the minimum should be -4.5 volts. The reason the reading goes negative is because the TCM converts the A/C signal from the VSS to the exact digital wave, therefore when checking the HZ signal on circuit 400 the fluke meter can be set on the A/C or D/C signal with hertz mode active. Circuit 400 can be checked by backing out the terminal at the ECM/PCM connector and placing the red lead of the meter to Circuit 400 and the black lead to ground. The signal from the TCM on circuit 400 will be the same HZ reading as the VSS approximately 28-34 HZ per 1 mile per hour.

The vehicle speed signal to the IPC, radio, cruise control module, and body control is provide by the ECM/PCM on Circuit 817


The second one


Condition/Concern:
ABS light on speedometer may be erratic. DTC C0055 C0235 C0236 or C0237 stored in the EBCM. This concern may be intermittent and not easily reproduced.

Recommendation/Instructions:
Using the Tech 2, check the ECM/ PCM and/or TCM for any speed sensor or communication related DTCs. These DTCs will need to be diagnosed first. Follow published diagnostics for related DTCs and evaluate the vehicle after repairs are complete. If no DTCs exist in any other module, inspect the rear VSS sensor circuit(s) from the rear VSS sensor to the related module (ECM, PCM or TCM) for integrity. These circuits are 821 and 822 or 400 and 401 depending on model and model year (use SI to locate the schematic that applies to your application). Repair or restring these two circuits as needed. Evaluate the vehicle.
Sorry, forgot you were very well versed on these as well.
 

Rockabillyrat

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I'm no transmission "expert", but electrical and communication issues are my specialty at work.

I've been inside of a few Allison's, but we are not set up to do transmissions at work. So we tend to sublet our rebuilds to a trans shop.
 

Odlaw

Redneck
Messages
568
Reaction score
17
Location
Deep in the woods - near Waldo, FL
Here are the test procedures for the issues your having. TCM issues are not uncommon with thoes.


1. Verify battery voltage is present at the "ACCY, On and Start positions of the ignition switch on the Pink wire at pin 63.

2. Verify battery voltage all the time at the Orange wires at pins 10 and 70.

3. Verify a good ground on the Black/White wires at pins 9 and 69.

4. If OK, check the resistance between pin 6 and pin 14 of the DLC with the key OFF. It should be 60 ohms +/- 10%.

5. If OK, replace the TCM. Programming is required after installation.


Also gm issued a few TSB help diagnose this issue. Here they are...

Condition/Concern:
Vehicles equipped with the Allison LCT1000 Automatic Transmission may exhibit one or more of the following conditions:

DTCs P0721, C0237, P0500, C0055

Speedometer inoperative, erratic or drops out

Cruise control inoperative

Radio speed control volume (SCV) inoperative

Transmission shifting concerns

ABS light illuminated

The following diagnostic approach may be helpful in repairing any of the above conditions.

The testing should begin at the VSS sensor located in the rear of the transmission on 2WD models and in the transfer case on the 4WD models. An erratic signal caused by a loose or damaged reluctor wheel can cause any of the above concerns.

Recommendation/Instructions:
On vehicles equipped with the Allison LCT1000 Automatic Transmission, the VSS signal is sent to the Transmission Control Module (TCM) via Circuits 821 and 822.

The signal from the VSS to the TCM is an A/C signal that produces approximately 28-34 HZ per 1 mile per hour. This signal can be checked using a Fluke 87 (DVM) set on the A/C voltage scale with hertz function activated and connecting leads to Circuit 821 and 822.

The TCM converts the VSS signal from an A/C sign wave to a digital wave. The TCM sends out approximately 4.5 volts on Circuit 400 to the PCM/ECM. With the vehicle stopped, the DVM will read approximately 4.5 volts on circuit 400, but once the vehicle begins to move the voltage will drop to near 0 volts. To check the voltage with the DVM with the vehicle moving, the min/max function should be set to 1 ms, the max should be 4.5 volt and the minimum should be -4.5 volts. The reason the reading goes negative is because the TCM converts the A/C signal from the VSS to the exact digital wave, therefore when checking the HZ signal on circuit 400 the fluke meter can be set on the A/C or D/C signal with hertz mode active. Circuit 400 can be checked by backing out the terminal at the ECM/PCM connector and placing the red lead of the meter to Circuit 400 and the black lead to ground. The signal from the TCM on circuit 400 will be the same HZ reading as the VSS approximately 28-34 HZ per 1 mile per hour.

The vehicle speed signal to the IPC, radio, cruise control module, and body control is provide by the ECM/PCM on Circuit 817


The second one


Condition/Concern:
ABS light on speedometer may be erratic. DTC C0055 C0235 C0236 or C0237 stored in the EBCM. This concern may be intermittent and not easily reproduced.

Recommendation/Instructions:
Using the Tech 2, check the ECM/ PCM and/or TCM for any speed sensor or communication related DTCs. These DTCs will need to be diagnosed first. Follow published diagnostics for related DTCs and evaluate the vehicle after repairs are complete. If no DTCs exist in any other module, inspect the rear VSS sensor circuit(s) from the rear VSS sensor to the related module (ECM, PCM or TCM) for integrity. These circuits are 821 and 822 or 400 and 401 depending on model and model year (use SI to locate the schematic that applies to your application). Repair or restring these two circuits as needed. Evaluate the vehicle.
All test OK except for pin 6 to 14 on DLC, ohms were 120
 
Last edited:

Odlaw

Redneck
Messages
568
Reaction score
17
Location
Deep in the woods - near Waldo, FL
Here are the test procedures for the issues your having. TCM issues are not uncommon with thoes.


1. Verify battery voltage is present at the "ACCY, On and Start positions of the ignition switch on the Pink wire at pin 63.

2. Verify battery voltage all the time at the Orange wires at pins 10 and 70.

3. Verify a good ground on the Black/White wires at pins 9 and 69.

4. If OK, check the resistance between pin 6 and pin 14 of the DLC with the key OFF. It should be 60 ohms +/- 10%.

5. If OK, replace the TCM. Programming is required after installation.


Also gm issued a few TSB help diagnose this issue. Here they are...

Condition/Concern:
Vehicles equipped with the Allison LCT1000 Automatic Transmission may exhibit one or more of the following conditions:

DTCs P0721, C0237, P0500, C0055

Speedometer inoperative, erratic or drops out

Cruise control inoperative

Radio speed control volume (SCV) inoperative

Transmission shifting concerns

ABS light illuminated

The following diagnostic approach may be helpful in repairing any of the above conditions.

The testing should begin at the VSS sensor located in the rear of the transmission on 2WD models and in the transfer case on the 4WD models. An erratic signal caused by a loose or damaged reluctor wheel can cause any of the above concerns.

Recommendation/Instructions:
On vehicles equipped with the Allison LCT1000 Automatic Transmission, the VSS signal is sent to the Transmission Control Module (TCM) via Circuits 821 and 822.

The signal from the VSS to the TCM is an A/C signal that produces approximately 28-34 HZ per 1 mile per hour. This signal can be checked using a Fluke 87 (DVM) set on the A/C voltage scale with hertz function activated and connecting leads to Circuit 821 and 822.

The TCM converts the VSS signal from an A/C sign wave to a digital wave. The TCM sends out approximately 4.5 volts on Circuit 400 to the PCM/ECM. With the vehicle stopped, the DVM will read approximately 4.5 volts on circuit 400, but once the vehicle begins to move the voltage will drop to near 0 volts. To check the voltage with the DVM with the vehicle moving, the min/max function should be set to 1 ms, the max should be 4.5 volt and the minimum should be -4.5 volts. The reason the reading goes negative is because the TCM converts the A/C signal from the VSS to the exact digital wave, therefore when checking the HZ signal on circuit 400 the fluke meter can be set on the A/C or D/C signal with hertz mode active. Circuit 400 can be checked by backing out the terminal at the ECM/PCM connector and placing the red lead of the meter to Circuit 400 and the black lead to ground. The signal from the TCM on circuit 400 will be the same HZ reading as the VSS approximately 28-34 HZ per 1 mile per hour.

The vehicle speed signal to the IPC, radio, cruise control module, and body control is provide by the ECM/PCM on Circuit 817


The second one


Condition/Concern:
ABS light on speedometer may be erratic. DTC C0055 C0235 C0236 or C0237 stored in the EBCM. This concern may be intermittent and not easily reproduced.

Recommendation/Instructions:
Using the Tech 2, check the ECM/ PCM and/or TCM for any speed sensor or communication related DTCs. These DTCs will need to be diagnosed first. Follow published diagnostics for related DTCs and evaluate the vehicle after repairs are complete. If no DTCs exist in any other module, inspect the rear VSS sensor circuit(s) from the rear VSS sensor to the related module (ECM, PCM or TCM) for integrity. These circuits are 821 and 822 or 400 and 401 depending on model and model year (use SI to locate the schematic that applies to your application). Repair or restring these two circuits as needed. Evaluate the vehicle.
correction, pin 6-14 are 60 ohms when you connect the tcm, 120 was with it disconnected.
 

Rockabillyrat

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There are two terminating resistors wired in parallel in the communication lines. If everything is connecting correctly then it will measure 60 ohms at 6 and 14. If you measure 120ohms then you have a open wire some where, or a failed module. You need to test all your communications wires between all the modules on that communication line. They are the tan and tan/white wires running from the DLC to the ECM, TCM, and GPCM.

Here are the test for the communication lines.


1. Access terminals 6, Tan/White wire and 14, Tan at the Data Link Connector.

2. Using an ohm meter, measure across the terminals and expect 60 ohms.

3. If the ohms reading is not 60 ohms, disconnect either the Engine Control Module or the Glow Plug Control Module and expect the reading to increase to 120 ohms. With either one of the modules connected, expect 120 ohms and with both modules connected, expect 60 ohms.

4. If the ohm readings do not comply, verify the wiring between the data link connector and the affected data lines between modules. The High Speed data bus is routed to the Transmission Control Module (TCM), Glow Plug Control module and the Engine Control


If your getting 60ohms with thr TCM unplugged. It sounds like that my be your problem.
 
Last edited:

Rockabillyrat

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If you have 60 ohm with all three connected the the communication lines are ok. Sounds like the TCM is bad.

I missed your correction post above🤦‍♂️
 

Odlaw

Redneck
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Deep in the woods - near Waldo, FL
Thank you for your quick responses. I was already leaning towards a tcm replacement. So, that brings up another couple of questions. Are pre-flashed tcm's the preferred route? Any site vendors sell tcm's? This one is for Fermanator, I'm still running the efi live tune you installed on my truck, will I need to get you to do anything tuning related with a new TCM?
Sorry, for all the questions, this TCM stuff is new to me...but man, glad I wasn't on vacation pulling my toy hauler - this would stop you in your tracks towing and it's not like you can run up to any auto parts store and pick up a new TCM.
 

Rockabillyrat

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I get all my modules from the dealership and flash them myself. But im a mechanic an have access to all the equipment to do so. I dont have alot of experience with pre- flashed stuff other than some of the early obd2 stuff that can come preflashed. But I know some performance companies offer pre-tuned TCMs for the allison.

If you had tuning done to the old TCM, the new one will need retuned if you by a stock TCM. If you buy a pre flashed & tuned TCM is plug and play since it already has performance tuning.
 

Odlaw

Redneck
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Deep in the woods - near Waldo, FL
As an example, I'm looking at the (new) pre-flashed TCM's at Ryan's Diesel service. Plug and play. $600.00, lifetime warranty. My time and towing to dealership are worth the additional $200-250 in initial costs...plus best warranty I've been able to find on a un-flashed TCM is 2 years, most are 1 year. And then there would be the $100.00 to the dealer to flash it. Seems like a no brainer to me but I will wait for some comments from you guys that have way more experience with TCM's.
 

Odlaw

Redneck
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Deep in the woods - near Waldo, FL
The new TCM from Ryans diesel is supposed to be here tomorrow afternoon. The last paragraph of the description is what I'm not sure about. Ferm tuned my truck with efilive, not sure if the tcm is tuned separately, or gets its info from the ECM via the DSP5 switch. I will update once I get it installed. Thanks again guys for your help.

BENEFITS TO OUR TCM OUR PRE-PROGRAMMED TCM'S COME RIGHT OUT OF THE BOX PROGRAMMED AND ARE PLUG AND PLAY THESE ARE THE LATEST CALIBRATION FOR YOUR TRUCK YOU DO NOT NEED TO TAKE YOUR TRUCK TO THE DEALER OR REPAIR SHOP FOR IT TO BE RE-FLASHED. SIMPLY REMOVE YOUR OLD TCM, PLUG IN YOUR NEW ONE AND YOU ARE DONE.

LIFETIME WARRANTY THESE ARE BRAND NEW UNITS NOT REFURBISHED

**IF YOU HAVE TCM TUNING WITH EITHER EZLYNK OR EFILIVE YOU WILL BE ABLE TO RE-INSTALL YOUR TUNES ONTO OUR TCM WITH NO PROBLEMS. IF YOU HAVE CUSTOM ECM TUNING THIS WILL SYNC WITH OUR TCM WITH ZERO ISSUES**
 

Odlaw

Redneck
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Location
Deep in the woods - near Waldo, FL
Well, I've been driving her for 5 days now without an issue. New TCM, did a couple of (what appeared to me to be) ally quick learn things, nothing crazy like before but firm shifts going into reverse initially, a couple of firm...ish downshifts from 2 to 1 at about 5 mph, not the tire sliding ones I've heard about, but not like normal. One thing I discovered (and I recalled reading it here in another thread that Ferm was responding to), was the 'CHECK BRAKE SYSTEM' code has to be cleared on it's own. Clearing it with my scanner just made it come right back after a bit of driving (but without the ill side-effects of the bad TCM). It would cause the engine to idle at 300-400 rpm for several seconds each time I cranked her up. It was kind of amazing that this beast of an engine could purr like a sewing machine at that low of an rpm and was seriously quiet. So, the next time the code came up, I just let it be and started driving. Once I got over 5 mph after a few seconds the code cleared on it's own, everything operating as it always has. I tried to include all the searchable particulars of this issue for folks down the road experiencing the same issues. A search of just the codes I was getting sent me down a lot of rabbit holes (on other forums). Even here, I struggled to find the exact issue so thanks to you guys with great responses and assisting me in troubleshooting this issue...hopefully, this thread will help folks.
Thanks again guys!
Smitty
 
Last edited:
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