Hi guys - i need some advice on how to trouble shoot a problem with my zeitronix ZT-3 set up. I installed it 9 months ago in a bung at the end of the DP just before the cat. Its mounted at the 10 o'clock position about 36 inches from the turbo. It's running the Bosch LSU 4.2 sensor. It is wired directly to the ECU and I have the red LED guage mounted in the clock on the dash.

Recently I noticed that the LED guage will occasionally jump to 14.7, and remain rock steady at that value for about 30 seconds, before dropping back to the normal changing AFRs. This corresponds with the steady WBO2 reading of 14.7 that I'm logging in Evoscan 2.9. It does this randomly throughout the operating range at varying loads and RPM. I've noticed that this is starting to happen more frequently. It used to be just once per drive and now it is 3 or 4 times per hour. This seems to indicate that something is gradually degrading either in the ECU, the zeitronix software, the wiring, or in the sensor itself.

The first thing I did to begin to trouble shoot this strange reading was to disable closed loop in the Tephra V.7 96530706 ROM I'm running. Periphery FAA bit 4 is set to zero. I run most of the time in open loop for economy cruise on E85 so my AFR map is already tuned for this. This has prevented the ECU from going in to closed loop at low load and TPS readings, and it now stays in open loop all the time. I'm still seeing the random 14.7 AFR readings logged in Evoscan

I don't feel the engine and ECU is suddenly going closed loop on me so I believe this may be a sensor problem. I guess this narrows the source of the weird readings down to the Bosch sensor, the wiring or the zeitronix software. How should I go about narrowing it down to root cause?

 

try re calibrating the sensor

 

Zeitronix sensors don't need to be calibrated.

 

Any suggestions on how to trouble shoot this guys?.........

How do wide band sensors normally fail? This is a bosch LSU 4.2. The ZT-3 unit converts it to 0V - 5V linear output. 0V = 9.6 AFR and 5V = 21.6 AFR. It seems strange that it would fail intermittently in the middle of the range..no?

 

i would just grab a new sensor. i have had 3 sensors fail (i have a bad mounting angle) and only 1 has failed the way everything says it will fail.

the lsu 4.2 can be had for 50 bucks at autozone if you dont mind the plug not matching (factory sensor for a lot of vw's and such)

 

Thanks for the feedback and suggestion killerp. I'll go and buy a new LSU 4.2 once I've talked to Zeitronix on Monday. Indicating stoich exactly could also be a problem with the ZT-3 control unit which sits between WB and ECU. Will post up results once I figure this out.

 

its a bosch sensor

 

from my notebook, just fyi.

difference in part numbers should just be wire length.

 

It was the sensor. Once I replaced with a new one everything works the way it should - case closed.