all my sensors bad?

[dsmcrazyspiff]

help mmcd working and gives me codes saying all my sensors are bad what is wrong

 

[awdtalontsi1992]

Is the car still running or is it dead? If the car is running normally then I would say it is a MMCd problem. However if the car is dead than I would say ECU is shot.

 

[blackbyrd]

I had the same problem, I was even throwing some CEL's that didn't exsist. My ECU was fried. Pull it out and check it for leaking capacitors or melted components(in my case) Oh and my car still ran, worth shit though.

 

[steve]

If the codes are for all the analog sensors then it's highly likely that the capacitors have leaked and damaged the ADC circuit in the ECU or the sensor ground trace is blown.

It's common enough that I've fixed a couple dozen times.

Steve

 

[dsmcrazyspiff]

car runs good sometimes and not others, two ecus both do the same thing one i know worked good

 

[DarthBulk]

Here is another possibility. Most all of your engine sensors get power from the same relay. If that relay is not turning on, your sensors will be unpowered, and all will read bad. The relay is under your radio, and is combined with the fuel pump relay, I believe.

 

[blackbyrd]

Did you check the wirring harness to the ECU, and all the wires? Check for breaks, loose, corroded, previously tapped into connections? Also check the wires at the ODB port. Are you throwing a CEL?

 

[dsmcrazyspiff]

yes i checked and all the wires are good . and it is throwing a cel ### it thinks the sensors are bad

 

[steve]

It is throwing a cel ### it thinks the sensors are bad

Which CELs is it throwing?

Steve

 

[dsmcrazyspiff]

all of them sometimes it shows like 16 codes

 

[blackbyrd]

Here is another possibility. Most all of your engine sensors get power from the same relay. If that relay is not turning on, your sensors will be unpowered, and all will read bad. The relay is under your radio, and is combined with the fuel pump relay, I believe.

I don't know about any ECU relay.. Never heard of it.. Couldn't find it in my manuals. The only relays listed interior is Door Lock, Starter relay(mt) Theft Alarm, Defogger, Seatbelt, and two daytime running light relays(for canadian models only)
The fuel pump relay? Isn't that the MFI relay? Under the hood.. On the battery..
Either way I'm going to pull my radio to check this out, haha.

How do you know the ECU was working good(the one you tried out in there?) I really cant see there being another problem besides the ECU, in this case.. Slight possibility it's a wirring issue.. I'd double check over all of that.

 

[DarthBulk]

It is not an ECU relay, the ECU just turns it on. I believe it is called the MFI relay, as you said. But it is under your radio. Both the fuel pump relay and the MFI relay are in one relay package, under the radio. One of the relays in that package provides power to almost all of the under hood sensors. I had a problem with my AEM not turning on this relay, and it caused a whole host of problems, all of them because the sensors were unpowered.

 

[blackbyrd]

MPI* is what I meant.. I'm doing some reasearch, I wasn't thinking when I typed earlier, the MPI FUSE is on the battery, not a relay. I also found out that the MPI Control unit, is run off the Battery fuse, in your main fuse block. I'm assuming it refers to the MPI Control Unit as the ECU. Yes It does look like theres a relay down there, odd I've never noticed it before(Thought the relay was only there on 2g's). Even odder the manuals didnt mention it! I did find the manual mention the connector for it(in a wirring diagram), but not the relay itself..

Check it out! Darth Bulk may be right on that one. Good information! you learn something new everyday, haha.

 

[steve]

Guys, you need to look at the wireing diagram. The MPI relay powers half the engine bay directly or indirectly via the ECUs 5v sensor power. The Ignition circuit powers the other half.

Only three sensors are directly powered from the MPI relay, the MAF and the two in the CAS. Everything else uses the ECU's 5v sensor power which is indirectly from the MPI since that's where the ECU get's it's power to run.

It's not likely the relay if the ECU is powering up.

Steve

 

[DarthBulk]

I have looked at the wiring diagram, intimately. I traced the power from this relay to every place in the engine compartment when I was trying to troubleshoot what I thought was a defective CAS. With the AEM EMS, when this relay does not turn on, a lot more is affected in the AEM because there seems to be a floating voltage problem. I don't know if it is the same for a factory ECU, but even if the MPI relay only powers those 3 sensors, as you say (I don't have the diagram in front of me, and it has been a while since I traced all these wires in the car), the floating voltage problem in the AEM affects a lot of other things. That is why I said this could be a possibility, not a definite answer.

 

[blackbyrd]

I'm a little confused if you trace those wires on the diagram, besides the Air Flow Sensor, and Crank and TDC sensor, doesn't it also goto the Oxygen sensor? It looks like it powers other things besides those sensors as well, but yeah, so what do you think it is steve? Could it only be ECU?? Just trying to help this guy out.. and maybe learn a few things in the process, haha.

 

[dsmcrazyspiff]

the other ecu i tried came out of a good running car i had so i know it is good or atleast good enough to run on smothly

 

[steve]

I'm a little confused if you trace those wires on the diagram, besides the Air Flow Sensor, and Crank and TDC sensor, doesn't it also goto the Oxygen sensor? It looks like it powers other things besides those sensors as well, but yeah, so what do you think it is steve? Could it only be ECU??

The O2 sensor heater is on the MPI circuit but the sensor itself isn't powered, in addition not all the sensors in the MAF use 12v, only the airflow meter.

There are several things that could be causing this problem and one is that the logger cable has problems. Like I said earlier cap damage can cause it but that sounds less likely if he has two ECUs doing the same thing.

Is your CEL lit on the dash?
Have you tried reading the codes using a multimeter like shown on the VFAQ site.

 

[dsmcrazyspiff]

no . do u have the link?

 

[DarthBulk]

The main vfaq site is here

http://www.vfaq.com/index-main.html

Just click on the 'Electrical' link there, and you will see the link for how to retrieve the codes there.

 

[blackbyrd]

http://www.vfaq.com/mods/wayback/BradBauer/electrical/code.html
You can either use a voltmeter, or goto radioshack and pick up a buzzer or light..
Haynes also has a tutorial for retrieving your diagnostic codes.

 

[dsmcrazyspiff]

Ok i figured out my problem it was the stupid usb adapter causing all my codes and for the missing it was a bad injector thanks for all the help