I can't make a connection to the computer through the access port under the steering column.

ric17

I determined that the port lacks current. I have checked all the fuses that I can find. I found one fuse panel under the hood on the driver's side and one in the kick panel on the driver's side floorboard. The check engine light is on and I was told that is what is causing it. Has anyone else had a similar problem?

thecardoc3

Power should be on pin 16. There should be grounds on pins 4 and 5. Most code pullers require the vehicle power and grounds to turn on, but a self powered scan tool only needs the ground connections and the data lines to communicate. if you tell us what year and model your Mazda is, then we can tell you exactly which fuse supplies power to the data link connector.

ric17

It is a 2004 Mazda RX8. I am sorry that I did not provide that information in my first post. Thanks, very much for helping me.

thecardoc3

No problem. It's labeled the Room fuse in the left hand kick panel. It powers up a number of systems including the power door locks. Does your key fob work and lock and unlock the doors?

ric17

Yes, the key fob works. All the fuses in the kick panel appear to be good. Still no communication with the ECM. Could it be a body or engine ground?
Thank you
Ric

thecardoc3

You car has both high speed and low speed data networks. The high speed network is on pins 6 and 14 and you would measure between 1.25v and 2.5v to ground on each of them. The low speed network will measure 2.3 to 3.3v. These numbers are representations of how a voltmeter would display that moving square wave. Basically the meter averages what it sees and updates the screen. Since it shouldn't be at the high, nor the low voltage value you get something somewhere in the middle.

What is the symptom you are dealing with that you need communication? Depending on whether the car runs or not, and what works or doesn't work it's possible to figure out if the car should have communication or not.

BTW does the scan tool turn on? You have the power and the ground connections if it does. The fact that the doors lock and unlock proves that at least some of the car does have a good data network. The keyless entry module is on the high speed bus with the Instrument Cluster, PCM, TCM, EPS, and more.

ric17

My CEL lite is on and when the handheld scanner is connected to the port under the dash near the steering wheel, there is no communication to the ECM so I am unable to read it for the trouble codes. There is either not any power or as you mentioned previously there is not a good ground.

thecardoc3

Does the car run?
Have you tried a different scan tool?

ric17

Yes, the car runs and runs well. I am going to pick up another scan tool to try that.

ric17

I got the bad connection fixed now it is telling me that my left bank is running rich. It is one thing after another with this car. Any suggestions.

thecardoc3

Can you give me the long and short term fuel trim numbers under each of the following conditions? Idle, Light cruise (20mph), Moderate cruise (60mph),

Under a full throttle acceleration (you need to have a snapshot of this to replay from both an accuracy as well as a safety perspective) how high does the engine load data pid go?