Help..my A/T won't shift. - Transmission Problems


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Help..my A/T won't shift.

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Auto Repair Home>> Automotive Repair>> Transmission Problems

rhodeback
New User

Jan 15, 2007, 1:09 AM

Post #1 of 3 (1799 views)

Help..my A/T won't shift.	Sign In

Hello All,

First time poster.

I have a 2000 Mazda MPV LX with 79,000 miles. We bought it in Dec. 2002 when it had 13k. It has been regularly serviced with oil and filter changes every 5 - 7 thousand miles, one coolant change, and A/T oil drained from the A/T drain plug.(about 2 quarts) with every engine oil change. The A/t pan has never been opened. A/T fluid is good..full and pink...no burnt smell.

This A/T problem just started...no warning...nothing unusual except a random humming noise when cold and coming to a stop or stopped. That humming seems to be echoing thru the air filter housing. I can hear and feel it there...it was in "P" with the hood opened when I noticed it.

The A/T won't shift upshift or downshift...I have to shift by shifting it manually. It seems to take off in D or second from a stop. Reverse seems normal. Also there is no shift indicator, so you can't tell by looking to see what gear the tranny is in. Also, there is no speedometer to indicate what speed you're going when moving. I took a wild guess and changed the inhibitor switch.....wrong! And it was a PIA to change too!

Thanks for any help you guys can give me!

rhodeback

steve01832
Veteran
steve01832 profile image

Jan 28, 2007, 3:30 AM

Post #2 of 3 (1764 views)

Re: Help..my A/T won't shift.	Sign In

Check out the vehicle speed sensor and its circuit. It controls the speedometer and also tells the PCM the vehicle speed. If the PCM can't see how fast the car is going, all shift points are defaulted.

Steve

rhodeback
New User

Jan 29, 2007, 1:51 AM

Post #3 of 3 (1759 views)

Re: Help..my A/T won't shift.	Sign In

Steve,
Thanks for the reply. I found the 15A cigarette lighter fuse blown last Wed. Popped in a new one and got my shift indicator back. Roadtested it...fine 'til Friday night...about a day and a half or 30 some miles. Popped again driving home and had to manually shift it back home. It's a dead short now. Popped the fuse as soon as I pushed another one in. Possibly the harness is rubbing somewhere under the dash? It was raining and I moved the manual heater controls from floor to defrost and floor before I left that night. Ok for about 10 miles...until I made a right turn. Trying to get a Hayne's or Chilton's Mazda service manual. Hope they have a wiring schematic! I need to find whatever is in the cig circuit.

My local Mazda dealer parts dept. says "Speed sensor?" when I try to get a price and availability....sheesh.

TIA

rhodeback

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