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Weird AVI voltage from wideband 02 sensor

Posted: Fri Mar 12, 2021 12:41 am
by Shuriken
Brief prehistory:
I set the Elite 1500 a month ago in my car with made by myself PnP adapter harness and with an attached AEM wideband 02 sensor. Everything was working very well except too noisy Toyota's knock sensor. I bought Bosch flat knock sensor and decided to install it. Being that the stock knock sensor has one wire I made a separate two-wire shielded cable and route it to unused wires in my PnP adapter. Then problems had started.
At first, the new knock sensor shows from nothing to a very low (in my opinion) knock signal.

Knock.png


The wideband sensor went crazy: it was showing the correct lambda values on the gauge, but Haltech was reading insane values of input voltage (3,5-4,5V at 0.8-1.0 lambda).
I thought that AEM was broken but I checked it separately with a multimeter and its analog output voltage matches its gauge readings.
I should notice that I wired AEM to two separate pins: B14 for a signal ground (wired to AEM's signal-) and B12 (AVI6) for a signal input (wired to AEM's signal+). I mean that these two wires are separated from my adapter and the stock harness, so other wires can't affect them. They are directly pinned to the B connector.
I unpinned the new knock wire (to exclude interference with wideband lambda signal), I even moved the AEM's analog signal from AVI6 to AVI5, but no luck. It always shows 4.96V.

So, here are my questions:
- Why some AVI lines show 0,5V of input even they are in the air? See screenshot, AVI6 even isn't pinned to a wire on this screenshot.

WB2.png


- The same question about knock input. When I was doing tests I removed the knock pin from the connector and ESP showed me this. Why the knock input shows a signal even in the air? Especially interesting that it was 0, then it was some constant value, then 0 again on the running engine.

Knock1.png


- Do signal ground pins (B14, B15, B16) joined internally in the ECU?
- Should I join them together in my harness or they can be used separately?
- Is it possible that I burnt AVI input? Herewith ECU works as expected, the engine works without problems. It would be the reason but I re-wired AEM's signal from AVI6 to AVI5 (as I said above) and AVI5 shows the same behavior, other significant AVI (IAT, CLT, MAP) show correct values.

Thanks a lot!

Re: Weird AVI voltage from wideband 02 sensor

Posted: Fri Mar 12, 2021 3:50 am
by Shuriken
It’s always about lost continuity. DTM connector between AEM and Haltech had poor contact in the ground wire. I wrote start post longer then I realised what was wrong :lol: