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Discussion Starter · #1 ·
I have a 2001 Elantra GLS, 160,000 miles. These two codes come up on ny diagnostic tool.

P0422
Main catalyst efficiency below threshold (bank 1)
No symptoms at all

P1529
Customer snapshot request
Symptoms
Car will shift hard into third gear and stay there without shifting at all regardless of speed. Shutting the car off and restarting will sometimes fix, but only temporary. When car runs normal, it runs fine and shifts good. At speeds around 40 it seems to kick back and forth between 3rd and overdrive as if it can't decide where to be. Tried replacing speed sensor, but new sensor did not fix problem.

Fuel Sys 1 CL
Fuel Sys 2 NA
Calc Load 18.4
ECT 201
STFT B1 0.0
LTFT B1 -2.3
MAP 8.6
Eng RPM 3351
Veh Speed 22

EV flashing
O flashing





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Discussion Starter · #2 ·
One additional thing is that when I leave work, the p1529 code trips at the exact same place each time.
 

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P1529 is just the TCM code. It means the TCM has detected a problem and has signaled the ECU as such, but does not give a clue as to what the problem is.

P0422 has nothing to do with your transmission code. It means the O2 sensor senses too much oxygen downstream.

When is the last time you changed your transmission fluid?

You say you replaced the "speed sensor". My question is which one exactly. Who did that? The dealer?
 

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Discussion Starter · #4 ·
I replaced the input speed sensor back in June based on a post I read on here from someone who had an identical problem as mine. The tranny fluid is the next thing I am going to have done as it is dirty. Is that something that can cause this issue?


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Change the fluid. It's a wonder you still have a transmission. Input speed sensors are best changed along with the output sensor. You find them sold in pairs on eBay.
 

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0422 is a cat efficiency code.. likely PCM determined cat to be weak via OX waveforms seen by PCM

1529 is a TCM request to the PCM for use of MIL.. you now need to go a step farther and access the TCM for DTC.. determine what the real code is stored in the TCM, then proceed with repair.
 

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Discussion Starter · #7 ·
When I first replaced the input sensor, I also did the output. However, the problem was only fixed when I placed the old output sensor, it worked with just the new input. The lasted for a month and a half before the p1529 code was tripped again and the same problem occurred again.

I am already aware of what the codes say. I have read several posts on this forum of those who have the identical problem, but never read if there is a solution that was found. I am trying to find out what the possible causes are are before I go to the shop for 20 different things that it could be so I can have an idea of the cost that may be involved. This car is old and has a lot of miles, but when the code for the tranny is off, which it sometimes resets when I turn it off, it runs like a brand new car. The tranny shifts smooth as it should.

The sensors, input and output, came from ebay. I received a replacement input sensor for the first one I replaced, but it did not fix the problem and adding the new output also did not fix the problem. Is it possible that all of these are bad, or should I be looking at other problems that it could be?

Should the tranny oil be completely flushed or should I drain and fill?

The fact that it runs so good when no P1529 is present baffles me and I just want to know if any who have experienced this specific problem has found the solution.


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Hi Gman, I had gone through your post. I too came across these codes through one of my friends but not experienced yet. I would like to have some more details about these codes for the detailed. Could you please produce some more attachments about this for more detailed view? Thanks in advance.
 

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Like I said, P1529 means nothing really, other than it senses a problem. Like SBR says, if you want to troubleshoot that better, you have to find a competent Hyundai mechanic who cares enough to scan with a proprietary scanner (good luck with that, they hate working on junk cars, just want to sell you a new car a change oil). If you're like me, you do a pan dump and just change the fluid about 5 times over the course of a couple months. My guess is the bad fluid is you problem, and just doing a few changes will make a world of difference.
 

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1529 is the TCM knocking at the PCM door asking to use the MIL...

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P1529 - TCU Request for MIL On

General Description

The TCM can request activation of the MIL lamp via a communication line to the PCM.

This is only a request from TCM to PCM to turn the MIL on. The fault code is stored in the TCM. Select Transaxle system on the Scantool and monitor DTC related automatic transaxle system.

DO ALL REPAIRS associated malfunction with A/T.
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You need to access the TCM and recover the offending codes from the Transmission Control Module.

Here, pick a DTC, blindly replacing parts can get real expensive quickly..

P0703 Stop Lamp Switch(Brake SW) - Short(B+)

P0707 Transaxle Range Switch Circuit Low Input

P0708 Transaxle Range Switch Circuit High Input

P0712 Transaxle Fluid Temperature Sensor Circuit Low Input

P0713 Transaxle Fluid Temperature Sensor Circuit High Input

P0715 A/T Input Speed Sensor Circuit - Open or Short(GND)

P0720 A/T Output Speed Sensor Circuit - Open or Short(GND)

P0731 Gear 1 Incorrect Ratio

P0732 Gear 2 Incorrect Ratio

P0733 Gear 3 Incorrect Ratio

P0734 Gear 4 Incorrect Ratio

P0736 Reverse Incorrect Ratio

P0741 Torque Converter Clutch Stuck Off

P0742 Torque Converter Clutch Stuck On

P0743 Torque Converter Clutch Control Solenoid Valve - Open or Short(GND)

P0750 Low and Reverse Solenoid Valve Circuit - Open or Short(GND)

P0755 Underdrive Solenoid Valve Circuit - Open or Short(GND)

P0760 Second Solenoid Valve Circuit - Open or Short(GND)

P0765 Overdrive Solenoid Valve Circuit - Open or Short(GND)

P1603 Can Communication Bus Off

P1604 NO ID from ECU

P1723 A/T Control Relay - Open or Short
 

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Discussion Starter · #11 ·
I have some transmission fluid that says "Multi vehicle" but states on the back that it is for vehicles that require SP-2 or SP-3 among other types. It is made by Castrol. Is that fine to use?

Also, does the new fluid get added down the dipstick hole or is there a spot to fill it?


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If you want to use universal fluid it's up to you. I wouldn't because it's not recommended. Yes, you have to add fluid through the dipstick. If you want to go cheap, A good match for Walmart fluid is the ATF +4 stuff.
 

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Have we recovered any DTC yet from the TCM ??
 

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Discussion Starter · #14 ·
Did a fluid drain & fill. Got about 5 qts drained. Took the car out and went into limp mode again. One thing I have noticed is that the warmer the car is the quicker limp mode happens. It went into much sooner than it would had I started put cold. Don't know if that means anything.

Next course of action will be to call the Hyundai dealer.


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I had an old Volvo for years that wouldn't go into overdrive when it got warm. I solved the problem by installing a big trans cooler and got another 70k miles out of that transmission before I wrecked the car. Trans coolers are cheap and easy to install, the dealer will tell you that you need a new transmission as they don't open them up and work on them anymore. Another solution is to simply drive it around w/o overdrive and love it.
 

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Discussion Starter · #18 ·
I just talked with the tech at the hyundai dealer. The transmission code pointed to the output speed sensor. The connection had some corrosion and they cleaned it up. Also had a loose shift cable. Told me that they drove it 17 miles with no engine light. The tech is going to drive it home tonight to make sure it's good and call me in the morning. Cost me about $100 to fix.


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