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Diagnosing Transmission Solenoid Performance Trouble Codes

What causes a code to set? That is a broad question with many answers. Let's keep this example simple.
Wednesday, August 28, 2013 - 07:51
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What causes a code to set? That is a broad question with many answers. Let's keep this example simple.

Diagnosing transmission solenoid performance trouble codes can be confusing, to say the least. The ATSG tech hotline receives many calls throughout the day related to this topic, and typically the caller is searching for the answer to this question: “Is this an external or internal transmission problem that I can easily fix?”

Figure 1

To even begin to answer this question, we need take some time and look at some of the components and criteria that a transmission controller is monitoring to set a solenoid performance code. As you probably already know, there are numerous differences between manufacturers and transmission types, so we will be looking at a specific transmission and its operating system to try to keep it simple.

First things first, what is the definition of a solenoid performance trouble code? I am going to go out on a limb here and give a semi-generic description. A solenoid performance trouble code typically will be explained on a scan tool as a solenoid, and its hydraulic circuit, that is either stuck off or stuck on. Some manufactures might just call it a solenoid performance trouble code without any clues as to whether it is stuck off or on. A solenoid and its hydraulic circuit pertains to the solenoid and the oil that is feeding it and the solenoid control pressure, which might control a clutch directly or indirectly through a clutch regulating valve. So what we are looking at is one solenoid and its mechanical performance, which also includes the ratio of the commanded gear. After all, when a solenoid or combination of solenoids are commanded to provide a specific gear, the control unit will need to see this gear by monitoring speed sensors which calculate the ratio.

Figure 2

This now brings up another question. Could a clutch that has a leak or a set of smoked frictions in it cause this performance code to set? Absolutely. Could this be a problem with the solenoid itself? Yes, it very well could be, but often times it is not. So we don't want to just throw a solenoid, or in some cases a new Transmission Control Module (TCM), with all new solenoids at this transmission just to see if it sticks and solves the problem.

Are these codes electrical in nature? Usually not, as the definition pertains to a mechanical problem. But there are a few exceptions, specifically with solenoids that have valve trains or pintle pins at the end of them that are not serviceable. If they are stuck, the solenoid will have to be replaced. Caution: If there is a solenoid circuit fault, such as a solenoid short to power, a solenoid open circuit or a solenoid short to ground code that is accompanying a solenoid performance code, we need to fix this first. After all, if the solenoid electrical integrity is faulty, we can’t expect that the solenoid is going to function mechanically. Scan tool PIDs can help you diagnose an issue with an electrical problem with a solenoid. Many pressure control type solenoids will commonly have a desired amperage and an actual amperage which will typically mirror each other when operating correctly.

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