June 17

2017 Mazda CX5 Transmission Repair


Mazda

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Mark: Hi, it's Mark Bossert. I'm here with Bernie Pawlik, Pawlik Automotive in Vancouver. Vancouver's best auto service experience. 25 times voted by their customers as the best auto service experience in Vancouver, BC, Canada. We're talking cars. How are you doing Bernie? 

Bernie: Doing very well. 

Mark: So today's victim is a 2015 Mazda CX5. What was going on with this vehicle? 

Bernie: Yeah, actually, I'll just make a quick correction, 2017. Anyways so the owner of this vehicle brought it to our shop. He'd had, in recent past, had the engine replaced with a used engine. The shop that did the job was no longer in business. There were some issues with it. The vehicle wasn't running well. The dash was lit up like a Christmas tree. Brought it to a couple other shops and they couldn't quite figure out what was going on. So they ended up bringing it to us for expert repairs, diagnosis and repairs. 

Mark: So what did you find? 

Bernie: We found that, you know, driving, it wasn't a very pleasant experience. There was some definite performance issues. And our first step was to hook a scan tool up to the vehicle scan it for codes and see what was happening. So the only codes we found, nothing for the engine, but transmission communication codes were present. So that's where we figured the area issue was cleared the codes and drove it. And the actual vehicle drove fine for quite a while until it started faulting again, and then it reset transmission codes.

Mark: So this is one of the intricacies of automotive diagnosis would be that sometimes things just aren't broken, it's intermittent. 

Bernie: Exactly. Yeah. And these are kind of the tricky faults to find, but, you know, once it occurred, we knew the area, we verified that the transmission was the area of concern. No engine codes. So from there, we focused our diagnosis on looking at what could cause the transmission to be at fault. And it was a lot of it was communication with the transmission control module, which is located inside the transmission, part of the valve body, which controls the shifting of the transmission.

So we examined wiring harnesses, connectors, voltages in various tests and found the problem with the connector going to the actual transmission, right at the valve body. And we could have a look at some pictures right now. 

Mark: Well, maybe just before we do that, this isn't necessarily knowledge that you guys have from experience or just stored in your own personal library. You guys have resources that you use to find out exactly what's going on because other people have reported this sort of issue across North America? 

Bernie: Yeah, we do. We do have access to resources like that. I actually didn't do the work on the car. I'm not sure my technician found anything. Because sometimes we're in, I like to think uncharted waters where, you know, we'll find something there's a particular code and our databases and all our resources, I mean, they'll tell us what the code is, but there's no one else who's actually fixed or repaired this particular issue. So we're kind of on our own to figure things out. And so I think that was the case with this particular issue. 

Mark: As we're going to see, it's a pretty unique issue. 

Bernie: Yeah, it is. Yeah. So there's a top view of the engine compartment with the engine cover on top. A couple of things to look at. If you can see the battery on the right side of the engine compartment, just in front of the battery, there's a couple of electrical connectors. There's two electrical connectors. And right below your box there, right at the bottom of that box. Those are two electrical connectors. That's where the powertrain control module sits.

2017 Mazda CX5 Transmission Repair


And so that's one area we inspected the pins of those connectors because when an engine job's done, those pins and those wires will be removed. Inspected all that. It all looked good. We tested further and found the actual problem was the wiring connector to the transmission control module, which is located underneath the air filter box, which is buried below the area where you have your box there. So yeah, underneath that area. So the air filter box had to be removed and we found the issue there. 

So this is a view of the connector to the transmission control module. If you can see all that green, very colourful, a lot of colour in there, it shouldn't be nothing but silver pins. And the blue arrow points actually to a pin that's gone. So there are two very large pins and these would be the positive and negative main power connectors. One of them, by the time we actually took it apart, it actually corroded so badly disintegrated. 

2017 Mazda CX5 Transmission Repair


If we look at the other connector ends, these are the old connector ends. The area that's all yellow is basically the pin stuck inside there, so it's broken off. 

2017 Mazda CX5 Transmission Repair


And you know, by the time we actually pulled the pin and connector apart, when we put it back together, the vehicle wouldn't drive anymore. So it was basically on its last legs when it arrives at the shop.

So there's a view of a good connector pin. We ended up having to replace that part of the wiring harness. And we had to replace the valve body transmission module, which is a pretty major component.

2017 Mazda CX5 Transmission Repair


So there's a view of the valve body. This is a bottom side view. If you look on the top, you can see black, those sort of round black pieces. So this is the bottom of the valve body. Those black round items you see with brown connectors, those are all the shift solenoids. There's several of them and these control the shifting of your transmission, which gear it's going to be in. Used to be done mechanically with springs and balls and little pressure sensors in the transmission. Now, it's all done electronically. The computer sends a signal saying, switch it into this gear and it clicks the solenoid and away it goes. Very accurate and much more expensive than the past. 

2017 Mazda CX5 Transmission Repair


So this is the top view of the valve body and at the bottom left of that black part, that's where that connector is located. You can't really see into it so well, but that would be the transmission control module. All the electronics would be inside there that send signals out to the rest of the valve body.

2017 Mazda CX5 Transmission Repair


Mark: So when you're doing a changeover like this, I imagine that you're going to change the fluid inside the transmission as well? 

Bernie: We do. Now transmission fluid, a lot of it is hidden in various places, such as the torque converter. There's usually a third of the transmission fluid sits in the torque converter. This fluid is very dirty. You know, it's not black or burnt. It's just old fluid. And definitely needs to be replaced. Now we could put everything back together, pour some fluid in a way we go. But in this case, we will actually you know, to complete the service, do a full transmission fluid flush on it as well, while we're in there doing everything else.

2017 Mazda CX5 Transmission Repair


Mark: So when we're looking at this kind of issue, as it's something that you haven't seen before, can you speculate a little bit as to the cause of this? 

2017 Mazda CX5 Transmission Repair


Bernie: Well, definitely it's had moisture, I'd say water get into this connector and that's usually the only reason why they corrode like that.

So the question is why is water getting into a, it's a weather pack connector. Weather pack is basically a sealed connector. It sits low in the vehicle, but it's designed that no water is going to get into this for years and years of driving. Now, the connectors do fail and it's possible it did. But you know, we would sort of speculate around the shop, what happened, probably when the engine job was done, it may have been the wires were left off for a while.

I don't know how long the engine job took. Maybe the hood was open. Maybe it rained. Maybe someone sprayed a pressure washer in there. Somehow water got in there. Then someone stuck it back together. I mean, it may have had nothing to do with it, but this connector would have had to have been undone to do the engine replacement job. So it's probable that someone let water get in there somehow, stuck it all back together, and we have what we have here. A very, very, very expensive repair.

So this is a view with the valve body removed. So we're looking up into the transmission. You can notice a lot of passageways on the left and right hand side, there's sort of the right and left, there's a number of sort of holes and openings. And this is where fluid flows through the transmission through the valve body. So, you know, it's under pressure. There's a pump and the transmission that pumps fluid through and operates the various components. And right in the centre, there's a clutch pack. You can see a clutch pack.

2017 Mazda CX5 Transmission Repair


These are what operate the transmissions various gears, depending on, you know, what's activated and what's deactivated. It'll put it to first, second, third, fourth, fifth. It's probably a six speed. I would guess in this vehicle. You get crazy. You know, some of them are 10 speeds now. There might even be more. 

I remember back when I was young, you know, there's like two speed automatics, there's a two speed power glide. And it's weird, like a two speed transmission seemed to actually work really well. Now there's ten. 

Mark: And even like bicycles used to, a ten speed was a big thing, and now that's like, that's one gear. 

Bernie: Yeah, I know. Yeah, exactly. The ten speed's like, that's not even enough. 

Mark: So, this is not a backyard job, obviously.

Bernie: No. I mean, diagnosing this stuff can be really tricky. The other thing we didn't mention is, you know with the module replaced with the new one and the connector all repaired, the module still needs to be programmed to the vehicle. So why it needs to be done. I don't know. I think like a engine computer should know. Hey, we plugged in the transmission module and away we go. But no, it's got to be reprogrammed for the vehicle. So this is just the way modern cars are. So yeah, it's not a backyard job. I guess you could do it in your backyard, but you'd end up having to tow it somewhere to get it programmed.

Mark: Right. And how did everything run afterwards? The whole problem really was the engine running, seemingly running rough and not, the car not operating properly was just this transmission connector? 

Bernie: Yeah, just the transmission. So it's very important and it's interesting on a lot of vehicles, it's hard to tell sometimes whether the issue is the transmission or the engine. I mean, we work on cars a lot, so we can kind of get an intuitive sense of what it is, but sometimes either one will cause strange operating issues. 

Mark: So there you go. If you've got a difficult issue, the guys to see are Pawlik Automotive in Vancouver, BC Canada. You can reach them on their website, pawlikautomotive.com. You can book right there. Or you can call them at (604) 327-7112 to book your appointment. You have to book ahead. They're always busy. Pawlik Automotive in Vancouver. Thanks so much for watching and listening, and thanks Bernie. 

Bernie: Thank you, Mark. Thanks for watching.

About the author 

Bernie Pawlik

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