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Honda-Man, Honda Mechanic
Category: Honda
Satisfied Customers: 3015
Experience:  I have an Associates Degree in Automotive. 10 Years experience on all makes and models. 20 Years Honda only including factory training. Over 30 years total.
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Honda Odyssey: We have a 2007 Honda Odyssey, with a VTEC engine.

Customer Question

We have a 2007 Honda Odyssey, with a VTEC engine. A little over a year ago, the Check Engine light came on. When this happened, the engine lost power. It sputtered. It had not acceleration at higher RPMs, just prior to shifting. The error codes indicated that the number six cylinder misfired. The dealership replaced the plugs. It ran fine for a year. About six weeks ago, it happened again. The Check Engine light came on. The engine lost power and started sputtering at higher RPMs. It would hard shift. This time, the number one cylinder misfired. There was also a battery charge system malfunction, which is probably not relevant. The dealership could not diagnose the problem, but wanted to change the fuel injector, but could not guarantee that it would fix the problem. We got a second opinion from an independent service center, which replaced the EGR valve. It ran fine for about a week. When we tried to tow an empty trailer, it happened again, about two miles from our point of origin. We took it to another independent service center, which specializes in Hondas. They had it for two days. They examined the valve train and could not diagnose the problem. The engine appeared to be running fine, so they returned it to us. About a week later, it happened again. It intermittently happens, on random occasions, with no apparent trigger or reason why. It can happen immediately when started, shortly after being started, after driving a period of time, or may not happen for days. It can happen when sitting still, or while driving, regardless of the speed. It can happen when it is nice out or in inclement weather. The engine does not seem run as smoothly as it used to, even when the check engine light is off. At the onset, just prior to the Check Engine light coming on, you can feel an erratic operation of the engine, then the Check Engine light starts flashing, then you have lost power, the engine has no acceleration, and begins to sputter at higher RPMs. During these periods when we encounter this problem, our gas mileage is reduced, significantly. I should add that the Check Engine light also flashes when we encounter these problems. I have notice, that on a rare occasion, when we feel the engine begin to operate erratically, if we accelerate, the check engine light goes off, and the engine appears to run smoothly. On a few occasions, we raced the engine in neutral, and the Check Engine stayed on, it ordinarily flashes, and the engine appeared to run fine. Some times when can turn the engine off, and turn it right back on, and the problem is resolved. Sometimes the vehicle can sit in the driven overnight, and the problem resolves. We recently checked the error codes, and now the one, four and six cylinders misfire. We also found and error code indicating that the barometric pressure sensor has malfunctioned, and that the ECM PCM has malfunctioned. The vehicle has about 150K miles. American Honda says that all we can do is take to a service center. We have ruled out plugs, coil packs, and fuel injectors. No one can figure this out, and it is becoming a costly endeavor. We are thinking about changing the barometric pressure sensor, to see what that does, or maybe the gas cap, to see if that has any effect.
Submitted: 2 years ago.
Category: Honda
Expert:  Honda-Man replied 2 years ago.
Welcome to JustAnswer. Do you happen to have the codes for the Baro and ECM/PCM malfunction?Just to be clear the plugs, coils, and injectors have been replaced or verified OK? Thanks! Honda-Man
Customer: replied 2 years ago.
I do not have those, as they were from past experience with the same problem. And yes, plugs, coils, and injectors have been verified OK. The service center yesterday, if trustworthy, could not determine the problem but said that the back bank of cylinders (indicated in my initial description of the problem) are not engaged, having to do with the VTEC technology, I presume. And, the same service center indicated that there is not compression on cylinder 1, but I suspect this is not trustworthy. I picked it up last night, the Check Engine light was on but not flashing. It otherwise operated as normal (i.e., it was not sluggish - it had power). About six miles later, the problem persisted (i.e., Check Engine light flashing, etc.). I am opposed to a shotgun approach. If we replace plugs, coils, and injectors and the problem persists, who reimburses us for the cost?
Expert:  Honda-Man replied 2 years ago.
That's OK I can look up the codes I just wanted to be sure. When you mentioned VTEC were you meaning VCM or variable cylinder management? It can have both systems but the VCM can case problems with spark plug fouling. I understand about the shotgun method too many techs seem to rely on it. The compression loss on #1 is got to be wrong. Compression problems don't come and go. Either there is compression or not. When the check engine l flashes that means the misfire is constant and can damage one or all of the expensive converters(3). Raw fuel from the misfire can overheat the catalytic converters. The only problem I see that has a diagnosable possibility is the Baro code and the PCM malfunction. The Baro sensor is inside of the PCM so if it's bad the PCM needs to be replaced. The PCM malfunction means it has failed a self test at start up and/or shut down. Both of these codes require PCM replacement. The PCM could be responsible for the misfire and poor performance. When it's misfiring this can be verified by checking the PCM control of the injector(s) and ignition coil(s) on effected cylinders. If the technician can duplicate the problem they can find the cause. Another indication of a bad PCM is the problem goes away if the ignition is cycled off/on like the PCM resets. Your problem just seems to be electrical in nature because it's so random and causes such a wide variety of problems. Please reply if you have any questions or anything to add. Thanks! ~Honda-Man
Customer: replied 2 years ago.
What is a PCM?
Customer: replied 2 years ago.
Powertrain Control Module? Is this different from the ECM? What's is the typical cost (parts and service) to replace this? If replaced and it doesn't correct the problem, what then?
Expert:  Honda-Man replied 2 years ago.
Powertrain control module. It's what can be called a ECM or ECU. It's the engine and transmission electronic control unit. Honda calls it a PCM because it controls both the engine and transmission. The PCM is approx $515 labor is approx $150 at the dealer. It requires programming so the immobilizer keys will work. Before it's replaced there are 2 Honda bulletins that should be checked. I don't think either one will help but they need to be checked before you spend the money just in case. Debris under the air filter can case the BARO(barometric pressure sensor) code since it can restrict the air flow. Removing the air filter and looking inside the housing will verify this. It can also cause driveability issues so it's worth a look. The PCM malfunction code can be caused by a loose connection at the inside fuse box. It's probably OK because it usually causes a no-start problem not just the code. The dealer will have this information and should have advised you on the possible solutions. If the 2 bulletins check OK the next step would be to replace the PCM. Like I mentioned before both codes are related to internal failure of the PCM. You can still come back for more information after providing a positive rating. Follow-ups are included i the original question price. Thank You! ~Honda-Man
Customer: replied 2 years ago.
I drove this yesterday afternoon, about 10 miles. The Check Engine light was on, solid, not flashing. This morning, I drove it about 30 miles, with the Check Engine light on. This afternoon, I drove it about 27 miles with the Check Engine light on, and then, within three miles of my home, it started flashing again. Today, it is damp (even occasionally raining) and cooler (about 72 degrees, as compered to the 90s with high humidity).
Expert:  Honda-Man replied 2 years ago.
Sometimes the weather can make a difference but not usually. Your problem is definitely random.
Customer: replied 2 years ago.
I am not yet ready to close this out until I have tried to implement the suggested course of action and determine if it remedies the problem. I have an appointment with a dealership this Friday. I will present this dialog, as well as documentation showing what else we have done to fix the vehicle. If in fact replacement of the PMU fixes the problem, we will promptly advise you.
Expert:  Honda-Man replied 2 years ago.
Sounds good, let me know what happens. Thanks