Heavy Metal! - June - 2018

2009 Honda Has Mysterious Noise and Won’t Shift Intermittently

So here we go again with a Honda with noises and weird shifting. In most cases, we tend to think that we’ve pretty much seen it all by now, but oh boy how wrong we are. When a vehicle comes into the shop, we pull codes and drive the vehicle to get a feel of the problem and whether it matches the customer’s complaint, which for the most part it never does.

So that being said, when customers experience transmission trouble nowadays, the first thing they do is Google it. Yep, times are changing rapidly and the number of auto experts out there keeps on growing. But when the customer brings the vehicle to you, more than likely he’s done research already, and is coming in with no exact answer and a gazillion opinions of what it could be.

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This particular vehicle was a 2009 Honda Accord with a 2.4L and a B90A. However, the same can happen on LX or EX vehicles with VIN CS1; or with an M91A unit on LX or EX vehicles with VIN CP2.

So this vehicle rolls into the shop. It intermittently won’t shift and makes a weird noise at times. Notice I said “at times,” because the wife claimed that, when she drives the vehicle, she doesn’t experience any problems. Obviously we have two different sets of driving habits: The husband drives the vehicle more aggressively than the wife. This is one reason it’s so important to pay attention to what the customers say.

This is valuable because, when it comes to diagnosis, those explanations offer a clue on where to go or how to drive the vehicle. It’ll make the diagnosis quicker, more effective, and more profitable.

Driving on an open road, tipping the throttle, the transmission shifted on time and there were no noises. Then, when we drove more aggressively, the noise showed up and codes P0720 and P0500 set.

Next we came to a stop, and started driving at light throttle. Once again the noise was gone and the transmission shifted okay. The issue is, when the engine is under torque the drivetrain moves back and forth.

I connected a scan tool and monitored the OSS and VSS. When we drive the vehicle slowly, there are no issues with the OSS or VSS and the signals are perfect. But when we drive the vehicle hard, the OSS signal goes berserk, and the codes come back, along with a screeching noise and an obviously skewed OSS signal.

With all that in mind, we decided to pull the OSS and inspect it. Eureka! Look what we found (figure 1):

So the OSS is grinding against the gear… or is it too long? Did this vehicle come from another shop or did someone else work on it? Well since metal noises aren’t normal in any transmission, we’re pulling this unit apart to see what we find.

We pulled the unit and tore it down on the bench. After removing the back cover and exposing the gears, we found a piece of a bearing had fallen off the housing (figures 2 – 4); bearing that supports the mainshaft in the back of the unit.

Since there was no major damage to any of the gears, the shop called the customer and gave him the choice of repairing the problem or completely rebuilding the unit. A simple repair turned out to be adequate for this problem.

So when the husband drove the vehicle, it put the transmission under load. That side-loaded the mainshaft, damaging the bearing. And with the bearing gone, the gear hit the sensor, causing the screeching noise and error codes.


Thanks to Steve Wilson at Gold Coast Transmission in Hollywood, Florida, for the pictures.