This is the solution that worked for me on a 2014 Lexus LS460.

After driving the car in very heavy rain and through flooded streets, the next day I got the message “Check the Power Steering” and the steering became very heavy. I scanned the car with an OBD device and got the code:

C1555 – Motor Relay Welding Failure

The strange thing was that if I cleared the code, the steering would immediately go back to being completely normal and smooth, with no unusual noises at all. But if I turned the car off for about 30 minutes or more and then started it again, the same code would come back and the steering would become heavy again. So every time I needed to use the car, I had to clear the code from my phone through the OBD app.

This strongly convinced me that the issue was not mechanical inside the steering rack itself, because the steering worked perfectly right after clearing the code. So to me, the most likely cause was an electrical issue, either in the wiring and connectors on the rack or in the EPS computer/module located near the battery.

The first thing I checked, just to rule out the rack itself, was the rack boots on both sides. These rubber boots protect the internal parts of the rack from water, dirt, and contamination. If the boots are completely intact, with no cracks, leaks, or tears, that is a strong sign that water probably did not enter the rack from the ends. This is important because it makes you suspect the electrical side more than the mechanical side.

Rack Boots


After that, I cleaned the three connectors on the steering rack itself.

These connectors carry electrical signals and power between the EPS computer, the steering motor, and the sensors inside the system. If moisture gets into them, the EPS system may detect a fault and store a code such as C1555.

first rack connecter

Second rack Connector

Third Rack Connector


Based on experience, it seems that one specific connector tends to get dirtier than the others, possibly because of its location, which makes it more exposed to moisture and dirt. That particular connector deserves extra attention during cleaning and inspection.

specific connector


Based on other people’s experiences, some of them, after cleaning and drying the connectors, add extra protection to reduce the chance of water getting in again, such as electrical tape or spraying a suitable protective coating around the area. But the most important thing first is proper cleaning and complete drying.

To be honest, I personally did not know exactly which connector was causing the problem, so I did not rely on cleaning just one connector. I cleaned all of them:

• The rack connectors
• The EPS computer connectors

That way I could rule out every possible source of moisture, oxidation, or poor contact.

After that, I also cleaned the EPS computer connectors themselves. The EPS computer is located on the left side, near the air filter box and the battery, and it has three connectors. I cleaned all of them using Electronic Contact Cleaner, then cleared the code again.

ESP module


There is one very important point from my personal diagnostic experience:

The problem did not disappear immediately after cleaning. The code kept coming back for about one full day. Only after the connectors had dried completely did the problem finally disappear and the steering return to normal.

To me, that strongly indicates that moisture inside the connectors was most likely the real cause. So if anyone tries this solution, they need to make sure the connectors are cleaned properly and then allowed to dry completely in the air. Even a very small amount of moisture can cause the code to come back again.

According to Lexus diagnostic procedures for C1555, if you clean the connectors, inspect the wiring, and the problem still remains, then suspicion starts to shift toward the EPS computer/module itself, because it may have an internal fault and may need replacement. Another possibility is that the wires or connectors themselves are damaged, weak, or corroded.

If you reach this stage and want to know for sure whether the fault is in the EPS computer or in the wiring/connectors, then you need a good automotive electrician. They need to check the EPS data readings and test the power supply, ground, and wiring with a multimeter, because at that stage guessing is no longer enough. Proper electrical testing is necessary.

As for the price, a new EPS computer from the dealer is expensive and may reach more than about $1300. A used one from a scrapyard or online may be much cheaper. Sometimes I have seen prices under $60 on Ebay, but you must make sure it has been tested and works properly, so you do not buy a part with the same problem.

EPS module


And here is my advice to everyone:

Be careful if a workshop quickly tells you that the entire steering rack is bad and needs repair or replacement, especially after water exposure. Sometimes that happens because of lack of experience, sometimes because of rushed diagnosis, and unfortunately sometimes because of dishonesty.

Because what may happen very simply is this:

The technician may know that the problem is only moisture in a connector, so he cleans and dries it, then the car works normally, and afterward he tells you that he “repaired” or “replaced” the rack.

In the end, the car owner pays the cost of a full rack replacement, plus labor, wheel alignment, programming, and all the extra expenses, while the real cause may only have been wet or oxidized connectors.

Sometimes even the mechanic who misdiagnosed the problem as a bad rack may accidentally fix the real cause without realizing it, because when he removes the rack, he usually disconnects the connectors and cleans the area indirectly. Then when the car starts working normally again, he assumes the rack was the problem, when in reality the issue may only have been moisture or poor contact in the connectors.

That is why I wanted to share my experience. Before replacing the rack completely, inspect the rack boots, check all the connectors, clean them, dry them very well, and inspect the electrical side first carefully. This may save you a lot of money and help you avoid unnecessary work.One extra

Emergency tip: if you ever get the “Check the Power Steering” warning and the steering becomes hard during the rainy season, and you do not have an OBD tool to clear the code or tools to disconnect/reset the battery, there is an emergency trick you can try.

Only use this temporarily and only in an emergency!!!!

When you press the start button to start the car, try turning the steering wheel left and right strongly at the same time. In some cases, this may help temporarily, but it is not a real fix and should not be relied on as a permanent solution because it will damage the the steering wheel. check this video it demonstrates the method

 

Excellent post, thank you very much! You clearly researched this deeply.

 

Thank you for this as well! give credit where credit is due.