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Alex, ASE Master Technician
Category: Car
Satisfied Customers: 1161
Experience:  ASE Certified Master Technician, L1 Advanced Level Specialist
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2000 Mazda MPV: cel trans) this morning..obd

Customer Question

the CEL came on in our 2000 Mazda MPV (6 cyl., auto trans) this morning. the codes from the OBD are: P1512,P0715.P0174 &P0171. Can you help with the probable diagnosis? thanks.
Submitted: 6 years ago.
Category: Car
Expert:  Alex replied 6 years ago.
Hello. My name is XXXXX XXXXX I'll be assisting you with your question.

The P1512 indicates that the Intake Manifold Runner Control Shutter Valve is stuck closed. This problem almost always indicates that the intake manifold runner control actuator is faulty and needs to be replaced.

The P0171 and P0174 usually indicate a failing intake manifold gasket that is causing a vacuum leak. The fix for this is to replace the intake manifold gaskets. However, with the 1512 present, I would be inclined to replace the intake manifold runner control actuator first and clear the codes and see what comes back. If the 171 and 174 come back, you will most likely need to replace the intake manifold gaskets.

The P0715 indicates a problem with the input shaft sensor on the transmission. This is another one that I would clear and see if it returns after taking care of the other codes. If the 715 does return, suspect a problem with the transmission input shaft sensor.
Input Shaft/Turbine Shaft Sensor Circuit Malfunction
Customer: replied 6 years ago.
Thanks for the answer. I dropped off the car at my favorite mechanics shop today. He looked at the codes and I believe he understands the gist problem, at least at the high level. Like you, he said the 3 codes (171, 174 & 1512) were related, but further diagnostics with his "computer" was necessary to pinpoint the parts required.
My follow on question to the P0715 code is if it could be the transmission itself being "worn out". This vehicle never shifted smoothly from the day my wife bought it. It seems like my test drive today revealed a bit of slippage or hesitation when starting from a dead stop. Could that and the "hard shifting" into 2nd gear be caused by a just bad sensor? I dread the thought of having to replace or rebuild the tranny. What is your thoughts on that?
Expert:  Alex replied 6 years ago.
If you are actually experiencing transmission issues then the p0715 is most likely indicating a real fault. The most likely problem is with the transmission speed sensor itself.

Be sure to check the transmission fluid level and condition on the dipstick, and flush the transmission fluid if necessary. The fluid should be a cherry red color and should not smell burnt. If the fluid smells burnt or is brown in color you will need to have the transmission flushed with a flush machine. When checking the fluid level, make sure the vehicle is on a level surface and the transmission is in park.

Lastly, if the transmission fluid is in poor condition it will cause shift quality issues, but will not be the reason for the p0715. The p0715 is indicating a problem with the transmission speed sensor regardless of the transmission fluid level or condition.
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Customer: replied 6 years ago.
Alex,I though you would like to know your answers were mostly correct. Your diagnosis was also very close. Here's what they did at the shop:
1. Remove/replace transmission input/ turbine generator 2. Remove/replace Idle air control valve. 3. remove /replace left and right intake manifold runner controller fittings 4. remove/replace intake air duct. I would say you did very well considering you didn't see the car. The only surprise was the air duct was cracked. It was one that comes from the air filter I think he said. You would have seen that if you were there. The total cost for parts, labor & tax was $542.00 out the door. A fair price I think.
Thanks for your opinion.
Scott Hanna
Expert:  Alex replied 6 years ago.
Thanks a ton for getting back and letting me know what happened, Scott. I'm glad you got it fixed and at a fair price.