AEM wideband interrrence problems
Turbo Mini Forums

Hi, i have this gauge fitted to my car but is causing some problems with the ECU, when the car is sat with the ignition on (ecu and AFR powered up) the AFR causes the ecu to think it is having a crank signal making the coil fire and the think its doing 8000rpm, when the afr is unplugged this problem stops, i have changed the power source and the earth and still have the same problem.

some other points:

when the sensor plug is pulled out from the back of the gauge the problem also stops.

tried the guage outside of the car and it still has the same problem.

heres a vid to show whats happening

https://www.youtube.com/watch?v=qiINgmxWhsw

sorry im having problems with embbeding it :/

does anyone know what i can do to fix this?

Is the sensor cable running close to your crank sensor wiring? Is your crank sensor wire screened, and is the screen grounded at one end?

check the grounds, try seperating them if they are joined.

i gave it its own earth and its still the same :/ ecu has its own earth too, how far apart do the earths need to be? can the signals travel through the bulkhead very far?

hmmmm,

I would check what the voltage is that it being fed to the ECU from the gauge, it should track with the AFR value, down around 1v at 10:1 about 2.5v at 14.5:1 and near 5v at 20:1.

I suspect the lambda heater current is getting into he ECU some how, i belive the heters are normally feed with a PWM current, so could trigger the crank input of the ECU.

At least you got an answer back, and one that appears to have been authored by someone who is not a muppet. That says a lot.
Could the issue be with your ECU actually causing the problem?

I agree with all the above, PWM generated noise from the LSU heater.

Usually, if it happens, it's a grounding issue but the "ECU" shouldn't be that sensitive if the crank sensor cable is screened.

By "ECU", the thing I see in the video is a "Nodiz" which I thought was ignition only so wouldn't have many other inputs or outputs ?

Is it metal cased and, if so, is it bolted down with a good ground connection between the case itself and the steel of the car ?

Although usually a ground issue, sometimes it's on the 12V side and caused by a poor connection somewhere like a bit of corrosion on ignition switch contacts or fuse holders or even bad crimps or soldering on the wire terminals. If the AEM and "ECU" are being fed from the same 12V source (ie, the ignition switch), separate them and see if it makes any difference. Ideally any ECU should be fed through a relay direct from the battery, picked up at say the main battery lead where it's bolted to the starter solenoid, with the relay being controlled by the ignition switch. It's also good practice to do the same with widebands because of the PWM nature of the heater power. Finally it's supposedly good practice to have all the high current grounds at the main grounding point on the engine block (earth strap between bodyshell and engine/gearbox on a Mini) but I've never had any problems using the bulkhead, just make sure all the paint is off and it's totally clean where you bolt the connection.

Schrödinger's cat - so which one am I ???

had a play around with it after work and still cant get it to work, earth it straight to the battery and still had the same problem, rang nodiz and they said that ive fitted the sheiled cable correctly and the gauge normaly works fine, so i might just bite the bullet and buy a new sensor

Where are you based? Is there anyone local that could lend you a sensor to try?

In the 13's at last!.. Just

i live in south wales, dont think any of you lot are around here :L

i have bought another one as i just want to get this car sorted, if it isnt the sensor i guess i have a spare haha