2001 Hyundai Accent sensor/transmission question



I have a Hyundai Accent 2001 with the “check engine” light on,

Yesterday I brought it to a local Garage for a oil change and

to have the engine codes scanned.

Come to find out I need a Oxgyn and Transmission sensor,

I also find out that the Transmission fluid is very dark.

The car has about 124,000 miles and the engine is great,

this morning a mechanic I know said changing the tranny oil may just

pose problems, I shoulld leave it as is and keep full?

I bought this car at 100,000 and have not changed the

tranny fluid, so I am not sure what to think here.

The Garage wants 400.00 to put the sensors in and

friend/mechanic said sometimes the

the code readings can be off, it may be one sensor

wreaking havoc?

I am just wondering what to do here?




What were the actual codes? If you have them, post them - or call/go back and get them.

The O2 sensor is likely a reasonable thing. “Transmission sensor” is vague. That’s why the codes are needed though.

As for the tranny fluid - I have heard every position on this. My own take has been that a) dirty/old fluid is a really bad thing. If it smells burnt at all then you really have to do something with it. And b) if a transmission is in such bad shape that a fluid change will wreck it, then its going to go soon anyway. That doesn’t necessarily go for a “transmission flush.” Many people will tell you not to do that. But a couple of pan drops w/ a new filter in the next 5k miles or so may go a long way toward gently cleaning up your trans fluid.

I agree with both suggestions, but I will add this.  Many drivers never think to change transmission fluid until there is a problem.  Guess what, changing fluid seldom fixes a problem.  They end up with new fluid but still have the problem that resulted from not changing the fluid soon enough.  Now the transmission goes out, which it was about to do anyway, and someone blames it on changing the fluid rather than their negligence for not changing it before the damage was done.


Exactly - which is why I’ve always assumed that many shops will say not to change trans fluid if it hasn’t been serviced regularly - they don’t want you back in a few days later blaming them for a trans problem.

So here’s an add-on suggestion - ask around for a good local transmission shop, and take it in for a basic diagnostic. Explain that you don’t know its maintenance history. They can hook it up to various gizmos to read codes that are present and also monitor the current operation of the transmission. This will likely cost you an hour’s labor time but it is worth it to do it. This is no guarantee that all will be right with the world, but its better than just having a garage replace a “transmission sensor.”


Your bigger problem is that the timing belt has, most likely, been neglected, also. Unless you have documented proof that the timing belt has been changed, it has to be considered original. The timing belt has 124,000 miles on it, unless the original owner changed it at 60,000 miles, which I doubt. If the timing belt is, indeed, original, it could go any day.
The engine in the Accent (either size) is an “interference fit engine”, which WHEN the timing belt goes, will cause very expensive damage to the engine (internally).


Very good point - I will second the importance of looking into that immediately.


I went to Advance Auto Parts today
this is the scan results:

Global ODBll

DTC ( Codes)

EVAP Emission
Control System Leak (Small)

O2 Sensor
CKT Slow response
(Bank 1 Sensor 1)

Manf Cntrl Veh. Spd.
Idle Speed Control
Auxiliary Outputs

Input/Turbine Speed
Sensor A
Circuit No Signal

DTC Pending (Codes)

No Faults detected