Stays in second gear and reverse

CPS_307

MEMBER
1999 MAZDA MPV
3.0L
V6
2WD
AUTOMATIC
307,000 MILES

Read here the problem is the gearbox ECU. Assuming this is the transmission ECU not the engine ECU?

Sunday, May 5th, 2019 AT 4:17 PM

5 Replies

KASEKENNY

MECHANIC
18,907 POSTS

Hi CPS,

I read the post you are referring to and they are talking about the transmission control module. I attached a location for it. However, I would diagnose yours like they did, because the only having second gear is called limp in mode. It could be the control unit or it could be a sensor issue, or could need a complete rebuild.

Check the fluid and see what condition it is in. Do you have a scan tool to check for any codes in the system? If not, most parts stores will get your codes.

It may work out to be the same fix but I would try these basic things first because if you notice, that person replaced the transmission before checking anything else. That was a pretty costly guess.

Let me know what you find when you get the codes or check the fluid. We can work through it and if nothing else is found then it may be worth the guess at the module.

Thanks

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Monday, May 6th, 2019 AT 4:09 PM

CPS_307

MEMBER
3 POSTS

Thanks for the quick response KASEKENNY1! I will try to locate a code reader. I had no luck finding the transmission control module. I'm in New Zealand and I believe these cars are bought over from Japan. The right side front from the picture I have the power steering reservoir, washer filler, and coolant reservoir in front of the strut tower. The left side had the air box, main fuse box, relays and the diagnostic connector. I looked under the dash. A number of connectors under the driver side (right). And the ECU (I believe its the main one) on the foot rest area on the passenger side. At the meantime, the fluid looks clean and not burnt. However, it did have a prior coolant leak on the hose just above the transmission. Which leads me to suspect the transmission range sensor may be faulty when coolant leaked over it (the sensor with the shifter cable attached on top). I dissembled it to see if I can find anything. Other than dielectric grease, two tiny springs and some copper contacts that was it. After slapping it back together the two 10mm bolts for the sensor is slotted. Which I tried moving the sensor in different position but still no change with shifting. I am able to have first gear manually. But once it is in S or D only second gear is in operation.

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Monday, May 6th, 2019 AT 9:27 PM

KASEKENNY

MECHANIC
18,907 POSTS

I am sorry about that not being the correct location. Unfortunately, I don't have anything that shows a different location and don't see another vehicle option. There is obviously something different with these vehicles than ones here in America. Normally, they are not that different but unfortunately, I don't have any information on your version. I guess the best bet would be to ask a local shop if they can help locate it. Also, the fact that your gears work manually also points to the control module.

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Tuesday, May 7th, 2019 AT 5:52 PM

CPS_307

MEMBER
3 POSTS

Hey no worries! So this vehicle has the old style type diagnostic connector. Retrieved the code P0755 Shift Solenoid B Malfunction.

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Thursday, May 9th, 2019 AT 5:52 AM

KASEKENNY

MECHANIC
18,907 POSTS

Okay. Great. This means the controller is most likely not the issue. Attached is the diagnosis procedure. Basically, you need to go through the wiring and then test the solenoid. If they both pass then the control module is the issue however, most of the time it is the solenoid itself.

Let me know if you need more information. Thanks

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