ECT Code 69 Problem

[Dh93GS]

Hello Everyone,
This is my first time posting to your site, but not my first time visiting. I have a 93 MX-3 GS 1.8L which is stock. Most of you are probably aware on the 92-93 GS's there are 3 water sensors, green one, black one and one for the gauge. The green one (CTS code 9, I believe) checks OK, the gauge sender checks OK, however (through a series of unfortunate events involving power tools and a pressure washer ) The black one (ECT code 69) ended up at 31K ohms and cracked.
OK, I think the resistance was already that high, due to multiple driveability problems i have been experiencing. Crazy idle, ac cutting in and out, hard starting with a strong fuel smell just to name a few. Yet, it never set a code and it turned the fans on at the correct temperature. According to alldata the ECT sensor is wasted (@96 degF 1.7-1.8k ohms @207 degF 1.4-1.5k ohms). The CTS tested good (@68 degF 2.2-2.7k ohms @104 degF 1.0-1.3k ohms) I checked the wiring and found a broken wire in the harness, right behind the intake manifold in the bend, which took care of most of the running issues.
The Problem i've been having is that i cannot find a ECT sensor at any parts house with those specs. Napa, Advance, nor Autozone has one. I have seen many sensors online, but do not want to order one only to have the same problem. Local salvage yards here in Pa, have not been of any help either. No matter the color, green, gray, or black they all seem to have the same specs as the green/gray sensor I have tried four different sensors and the fans run right at startup followed by a CEL 69 code shortly after, like the ecu doesnt even see the sensor. I would clear the codes and try the next sensor with the same result. All connections have been checked and double checked. The voltages at the ECU are the very close (within 0.5-0.3 volts) for both sensors as well.
Although the plastic case is crack, reinstalling the original stops the light and fans. The running issues may return as well, but with the wire repaired they may not. If i can find where i threw it i will try.
So what do you all think, bad ecu?, alldata wrong, or does anyone know of a good aftermarket sensor to try with the correct specs. Mazda still has them, but I would hate to go to the stealer. Also, ordering stuff online makes it hard to return if not needed. The ecu could still be crap which i would like to get a backup anyway.
Let me know what you all think any help or advice will be appreciated.

[davmac]

Green and gray sensors are essentially interchangeable and provide input to the ECU for idle control. The green or gray sensors would have three ribs that mate with the connector and are the middle of the 3 temp sensors (just behind and to left of coolant filler pipe).

The black sensor should have only one rib to mate with the connector and is just to the right of the coolant filler pipe. The black sensor is used to control the radiator fan. I don't think this one will impact driveability.

Diagnostics code 69 could be high resistance or open circuit (infinite resistance). You may need to check some more wires to confirm it is not a broken wire that is causing the code.

I found it easier to find a replacement black sensor. Standard Motor Products TX40 is a common one that most parts shops can get or cross reference. RockAuto is a good online source that will take returns - though you'll eat the shipping charges.

[RX8SE3P]

It shouldn't be the ECU but I have had an ECU work without the fan issue then swapped to a different ECU of the same year and the fan problem had arisen.

The ECTF sensor should not cause it to run badly. Strange that some sensors set it off but the original one is fine. I say keep it if it works fine and you don't have the fans intermittently switching on and off constantly. This sensor should not cause running issues apart from the fan problem if faulty.

If you do source a newer ECU, beware that the distributor pin outs could change and your car may not start.

This is a great page for codes too - http://forums.beyond.ca/showthread/t-47452.html

[Dh93GS]

Thanks for the replies,
The black sensor is 3 ribbed as well, it actually is opposite the green/gray ribbed sensor so you cant mixup plugs. I reinstalled the original and have been able to drive it for a couple runs now; the drivability issues are gone and no lights. I think fixing the broken ground wire for those two sensors behind the intake took care of that. I have not tried the TX40 yet maybe i will give that a try. As far as a ECU i was just planning on getting a 93 model year used one to avoid any capatability issues. Now, I have to deal with the sputtering start cold and i'll be golden. (leaky Injector)
Yes it is strange that the original works and not the others. I did retest it before installing it, and it showed 15k ohms @96 degF. So i guess ill leave it for now. I have to contact the alldata rep to see if the data is accurate. The diagnostic flow chart for the code 69 from them was not accurate (showed testing the wrong ECU pin).
Thanks again for the replies, i will check back and update if i get anymore information. Thanks again.

[Daninski]

To start with welcome to the forum. Update your info so we can see where your from. Most of us have spare ECU's and would be willing to sell you one cheap. I think I have like 4. ECU's usually don't have problems but if you decide to buy one simply post in the [WTB] section here. $20 buck would easily find you an ECU here.