oL-70 Allison: What Does oL-70 Mean on Allison Transmission?

The old engines of the 20th century did not have error codes till later in the century. They were never needed as transmissions and engines were easier to fix and spot the problem. Sometimes one wishes technology did not improve engines.

The oL code is talking about fluid level for the most part. The 70 or other figures next to the oL is telling you about the fluid temperature. When you see the 70, that means that the temperature is too low. A 79 after oL is saying the temperature is too high.

To learn more about this error code, just continue to read our article., it has the information you want to know about so you can understand what your indicator lights are telling you. It is not all good news.

Allison's Transmission Code oL-70

Allison's-Transmission-Code-oL-70 (2)

The oL error code for the Allison transmission has several definitions. It isn’t just the oL that you need to know what the problem is. You have to read the letters or numbers in the box next to the oL to find out the problem.

When you see the number 70 after the oL it is telling you that the sump fluid temperature level is too low. If you see a 79 next to the oL, then that message is telling you that the sump fluid temperature level is too high.

But to get to these numbers and fluid level reading, you have to go through a simple process first. The process is found in the Allison shift selector code operator manual, found at this link. The process goes like this:

1. Park the vehicle on a level surface, shift to N (Neutral), and apply the parking brake.

2. Using a push button shift selector, simultaneously press the UP and DOWN arrows one time.

Using a lever shift selector, press the Diagnostics button one time.

3. The fluid level reading may be delayed until the following conditions are met:

Engine is at idle.

The fluid temperature is between 60˚C (140˚F) and 104˚C (220˚F).

Transmission is in N (Neutral).

The vehicle has been stationary for approximately two minutes to allow the fluid to settle.

The engine is at idle (below 1000 rpm – not “fast” idle).

You will have to scroll down a little to get to the page that has this information as well as any pictures that will help you understand why you can’t drive. The system that is a part of the Allison transmissions these days will also tell you how many quarts of transmission fluid you need to add.

All the information is at that link and it doesn’t take long to read it. Then scroll down a little further and you will get to the numerical portion of the error code.

What Does oL-70 Mean on Allison Transmission?


Once you have done the above, you may find that you still have a problem. Here is what the manual says:

Invalid for Display – If any of the previous conditions are not met, the shift selector will display “oL” (“oL” represents “Fluid (Oil) Level Check”) followed by “– –” and a numerical display. The numerical display is a fault code and indicates conditions are not proper to receive the fluid level information or there is a system malfunction.”

Following that paragraph is a little table telling you what the numerical codes mean. The 70 is about halfway down the table and it is not hard to spot. It just tells you that the sump fluid temperature level is too low.

If you read a 79 in the numerical spot, then you have a temperature level that is too high. Underneath the table, you will see a warning telling what could happen if these error codes are not fixed.

There is a drawback to this manual though. It is only a manual to tell you what the error codes mean and how to access them. The manual does not tell you any solutions or what you should do when you have this problem.

The manual simply tells you basic information and you would need to talk to a mechanic or look in another manual to learn what you need to do to solve the problem.

How do I Clear My Allison Fault Code?


The process seems straight forward but it may be a little hard to write all the instructions down so they are understandable.

Bellow there is a video that shows you how to reset the codes as well as some verbal instructions.

In this case, seeing and hearing is better than reading. The manual that we linked to does not seem to have any instructions for resetting or clearing the codes. It may be there somewhere but it is not on the initial pages we linked to and quoted.

According to another site, you just have to press the mode button for at least 10 seconds to clear all codes. If you want to reset the indicator light, follow these instructions:

- To reset the service indicator light.

- Turn the key on, do not start the engine.

- Move the shift selector to N-D-N-D-N-R-N, pausing briefly (less than 3 seconds) between each selector movement.

Or if you are still unsure or these methods did not work, talk to an experienced Allison transmission repairman or the vehicle dealer. They should be able to give you more information on this process.

Some Final Words

Modern engines and transmissions have more codes than you can imagine. The trick is to understand them all so you do not make a repair mistake. In this case, the error codes are easy to understand.

Unfortunately, the manual does not give you any instructions on how to solve the problem. To solve these issues, just talk to an experienced mechanic or go to your dealer.

They should be able to fix the problem and have you on your way again. Sometimes, these codes make you wish you had a 1960s or 70s transmission in your vehicle.

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