Hi guys,

In process of tuning my AP1 TTS Supercharged with the world famous AP1Chief I am having a strange issue : the AEM EMS V1 is reading very buzzing values on all the sensors/inputs !

My car setup is:
AP1 MY 2002 UK RHD
F20C MY2004 engine
AEM EMS Series 1 (30-1052U)
TTS Performance C30-94 kit
RC Engineering 750 cc injectors (SH4-0750 - 12 ohm)
Walbro 255 fuel pump (oem wiring)
Fresh NGK BKR8E-11 spark plugs (resistor) with oem coils
AEM UEGO 30-4110 with LSU 4.9 - 0-5v output of the UEGO gauge connected to the Lambda#2 pin of the AEM EMS
Prosport oil temperature + pressure gauges (sensors on sandwich plate; sensors grounded in engine bay)
Those 3 gauges are powered by the "ing on" free pin on the fusebox, with a 10amp fuse, and grounded to the existing ground point near the fusebox where already several things are grounded

Now, the facts:

1. Before installing all this stuff, my car had no visible electrical problem. But I had no EMS to see if values were buzzing or not...
2. Now with all that stuff:
   1. values in EMS are constantly buzzing/jumping
   2. when driving the car, I sometimes have CELs flashing: the green key and the orange engine. See this vid:
      You Tube
      In the tune, the LS10 output (engine CEL) is configured to light above 205F: with values buzzing, this can be a reason for it to light... (I saw sometimes 205+ values in the logs due to buzzing).
      But for the green key, I have no idea! What is the output LS number ?
3. All that parts (SC kit, EMS, walbro, injectors) were, 1 year ago, installed on another AP1 MY03 UK , except:
   1. spark plugs that were different (don't know the model),
   2. UEGO gauge output that was not connected to the EMS,
   3. oil sensors that were not installed (but gauges were... useless ).
   4. The EMS tune was different: it was made by a french tuner. Now the actual one is completely new and being made by AP1Chief.
4. I drove this previous car for about 1 month and I freduently noticed those same CELs flashing , sometimes at WOT, sometimes cruising on highway at 85mph 6th gear... never in the same conditions in fact.
   I did not connect to EMS on this previous car so I can't say if values were buzzing.

Troubleshooting:
Does anybody have any idea of what can be happening ?

We have thought of electrical Gremlins, but the fact that CELs were already flashing on the previous car makes me think it is not a ground problem on my car.
To be sure of that:

• I will change the (fresh new) spark plugs for my old NGK PFR7G just to check if the new ones are not creating gremlins.
• I will remove all my gauges power and ground wirings, just to check if the new ones are not creating gremlins.

And the question I really fear : do you think the problem can be inside my EMS ?

Thanks for your help

 

Here is an example of my buzzing logs during a pull:

 

Known good AEM EMS V1?

If it did the same on another car prior to this car, it's likely not the car.

 

OR has something to do with the coolant sensor module you got wired up.

 

The modifry ECT module was on the previous car yes, and I installed it on my car also. But, yesterday I unwired it completely: I had used fast connectors like that, so it was easy to remove completely and without damage on the oem wiring.
https://www.picclickimg.com/00/s/MTAwMlgxMDAy/z/4T4AAOSw-xVaPLqL/$/50x-cordon-de-verrouillage-cable-electrique-connecteur-depissure-_1.jpg

And you saw like me that it made no difference

 

You sure no other voltage reference was being fed into the EMS when u disconnected everything?

sure does look like its the coolant sensor thats freaking out and causing issues.

 

The only thing connected to the EMS now is the 0-5v output signal from uego gauge.
I will try to completely disconnect power and ground wires that feed all my gauges (and by consequence, that send the 0-5v to the ems).

And this output was not wired to EMS on previous car...

 

yea try to discount all outside inputs to ems see if it goes away

 

- wires for my gauges are unplugged : power removed from the "ign" free plug in the fusebox, and ground removed from the oem-used ground screw near the fusebox.
So no gauge working, and no wideband power.
- spark plugs replaced with my previous NGK bkr7eix-11ps

And still the same
Now on video: first only with ignition on, and the starting engine. We can see battery volt, throttle, boost, air temp and coolant temp constantly changing.

 

Yesterday I did a few more tests.
Here is a log of startup and idling with my EMS v1, and the jumping sensors...


And here is another log I made on my car, but with the AEM EMS V2 of a friend (with his tune, so idling was really bad because we have different injectors and MAP sensor):