Inconsistent AFR's AEM X-series wideband

[TheLawProject]

Hopefully someone can help me find a solution. I have a p72 ecu, s300, and have wired the AEM X-Series wideband to D14, and grounded to the TStat Housing via the harness. The gauge and the display read the same, and I have entered the correct Voltage/Lambda Conversion numbers.

I do my fuel tuning in the open loop (closed loop disabled) setting. I can get it dialed in, then switch it over the Closed Loop. Not sure if I should be in Lambda target or Voltage target? It can be idling perfectly at 14.7 one minute, then turn the car of, give it 10 mins, and when I start it back up the AEM gauges is showing a much richer value. anywhere from 9:1 to 11:1. If i blip the throttle and start driving it seems to then get back to the 14.7 at idle.

Any advice or info is appreciated.

Thank you!

[Spunkster]

You should not use the D14 input as it cannot see the full voltage range. Use D10 instead.

[TheLawProject]

Do you think that is my problem? If I switch it over to D10, do I need to do anything else inside the ECU?

[TheLawProject]

The below information is from HAmotorsorts, the company I got my ECU and s300 from. I am using the LSU4.9 sensor too.


This ECU board modification will allow your OBD1 ECU to use the ECU pin D10 (ELD) for your wideband signal input. The advantage to using pin D10 instead of the stock O2 sensor pin D14 is that the ELD input is capable of processing a full 0-5 volt signal, while the D14 pin can only process 0-3.73 volts which will limit your air/fuel ratio datalogging ability of the wideband signal. UPDATE: With all newer wideband systems that use the Bosch LSU 4.9 sensor, 0-3.73 volts reading through the stock D14 O2 sensor input is more than sufficient for reading air/fuel ratio, so using the D10 ELD input is no longer beneficial. If your wideband uses the Bosch LSU 4.9 sensor, we recommend using the D14 input now, this way you can leave the ELD circuit functional.

[Spunkster]

The sensor you use does not matter. The controller that operates the sensor is still going to output a 0-5v signal. YOu need the full 0-5 volt range for this to work correctly.

[TheLawProject]

That being said, will I need to remove R136 and R138 in the Ecu?

thank you

[Spunkster]

Yes it is recommended to cut these resistors.

[TheLawProject]

One last thing... Will I need to reconnect d14? I am not using a stock o2 sensor, only the wideband.

Thanks.

[Spunkster]

No you do not need a stock narrowband connected.

[TheLawProject]

Am I taping into the harness of d10 or cutting it, and butt connecting to the ECU side, and leaving the harness not hooked up?

[Spunkster]

The ELD can no longer be connected. the wire must be cut or de-pinned.

[TheLawProject]

Okay, is there a setting in sManager that I will need to change besides the the input from d14 to d10? I assume I have to disable ELD under Misc Parameters?

Just so I'm clear, Am I connecting to the ecu at d10 or the connecting to the wire harness for d10?

[Spunkster]

Yes ELD error should be disabled.

It can be connected anywhere as long as it goes to D10 and the ELD is no longer connected.

[TheLawProject]

Once I’m done tuning in open loop, which closed loop setting should I use? Lambda target or voltage target ?

[Spunkster]

That is completely up to you, you can try both and see which works better in your situation.