QuestionQUESTION: Roland, my check engine light came on over a yr ago. I had it checked at a local garage and the dealership and both showed code P0443. They both said I needed a new computer for the car. I wasn't having any problems other than the check engine light and chose not to replace it. Now I live in a county that requires emission testing and cannot have it tested with a check engine light on. The local mechanic suggested getting a rebuilt ECM programmed with my VIN and mileage. I ordered one from ACE and installed it today. My check engine light is still on. I am not have any other issues except my A/C went out a few months ago. I took it to advance auto, autozone and O'Reilys to have it scanned and now the P0443 is not showing up, but P1491 and P0705 are. Any suggestions would be much appreciated.
ANSWER: Hi Theresa,
Let me finish getting dinner together and then get back to you later today. Thanks,
Roland
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QUESTION: Roland, take your time. Just knowing you are here to advise me is such reassurance. You have helped me many times in the past and never led me wrong. I should include that a smoke test was ran when the engine light first came on and did not show a leak. They checked the evap solenoid and said it was opening and closing correctly. They checked my computer by hooking it to another evap emission control system and said my computer worked okay with that one, but would not "communicate" with the one on the jeep. Both the local mechanic and the dealership reasoned that it was my computer going bad and needed to be replaced.
ANSWER: Hi Theresa,
The code that is causing the check engine light is the 1491. The 0705 says that the device inside the transmission that senses which gear you have selected is not always doing so accurately, but unless you notice a problem where the trans doesn't do what you ask it to do I would not worry about that code. That code doesn't affect the pollution output of the vehicle so it doesn't cause a check engine light to be illuminated.
The 1491 says that the circuit which operates the radiator fan relay is not working properly. Chances are that it is the fan relay itself that is faulty. Because I don't have Jeep manual I can't be sure where it is located. You could look at the power box in the engine compartment where you will find several relays and the diagram or lettering on/in the box may identify which is that relay. If you don't find the relay in the box, the go to the fan motor and follow the wires from it to the location of the relay where you will find those wires to be attached. It could be on the frame at the left side of the radiator, or actually around in front of the radiator mounted on the frame bar that runs below the radiator.
Once you find it, you could simply buy a replacement and exchange out the old relay. Then disconnect the battery - post clamp for a minute and reconnect which will erase the old fault codes and turn off the light. If the light doesn't come on then you have fixed the problem and can get it smog tested. If the check engine light does come on, then the wires from the computer to the fan relay will need to be checked. Also maybe the replacement computer wasn't exactly correct for your particular engine/year so verify that you indeed have the correct replacement computer. If that that 1491 is a new code that started with the computer replcacement I could imagine a situation where the computer is looking for 2 fan relays, but you only actually have one, or vice versa. But a relay that you buy and install yourself may be the least expensive approach to try as it doesn't involve labor. The 1491 code does turn on the check engine light so it will have to be cured to pass smog test.
If the red light comes on again get another code readout and let me know.
Roland
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QUESTION: The fan relay is in the power box under the hood. I will change it out in the morning. So does this relay control my A/C? If so, I can't really say the 1491 code started with the computer replacement because my A/C stopped working after the original scan that only showed the 0443 and I didn't have it scanned again until I installed the replacement computer. I have had no issues of overheating. I am concerned that the evap code did not appear at these locations when scanned last year. I was only able to get a read out at the dealership and a garage. Should I install my old ECM again and have another read out to see if the same codes appear before replacing the relay? Can I assume that the new ECM "fixed" the P0443 code? I can only assume it is the correct ECM for my jeep. I was told by the company it was and submitted my mileage and VIN for it to be programmed. It looks the same...
AnswerHi Theresa,
Have you noticed that when the engine temp gauge is moving toward H that the radiator fan is not coming 'on'? You can usually hear the fan and of course lift the hood to visually check its action or not. That non-activation when the gauge was high would be the symptom of a failed relay cicuit/failed relay. The request for A/C always causes a fan request regardless of the temp of the coolant. But since your compressor is not responding to the A/C request, that usually is due to running low on refrigerant. I don't know if the fan relay circuit goes bad whether that also circumvents the A/C compressor, or not. I haven't come across that as a reason for no A/C but it is possible. If the fan is working then I would wonder if the 1491 might be an inaccurate code readout. Unfortunately I don't have a Jeep manual for that time frame so can't be sure of how that circuit is specifically wired up. But if there is only a single relay for the fan, then that is pretty straightforward as to what you need to buy. Many vehicles have two speed fans with two relays involved. The bottom line is to get the check engine light 'off' so you can pass smog. I wouldn't know how to deal with the 0443 code now that it is gone...leave well enough alone?
Roland
PS Thanks so much for your rating and kind remarks. I also wanted to mention that it may be something as simple as a blown fuse that could cause the 1491 code. I don't have the wiring diagrams but there would be a 40 amp or so fuse that powers the fan motor (in the power box under hood) and a smaller fuse that powers the relay actuation coil. So do look over the fuses both in the engine compartment and under the dash (assuming both locations for fuses) before you buy the relay.
