Interpreting data. VS s3 Log

[MAGP]

I agree I'd fit both O2 sensors and swap over to a VT memcal. But he doesn't have a VT memcal and he has disconnected the 2nd O2 sensor so disconnecting the wiring from the PCM may help him in the immediate instance and may help others who do this swap in the future.

[MAGP]

VS 3 enhanced bin has an option for 1 or 2 sensors in the xdf just flag 1 or 2.

Just seen this post. This is very good to know. So in effect he could set the flag to 2 O2 sensors and run both. Much easier option than trying to find a VT memcal.

[yoda69]

Running a VT memcal in a VS3 will cause other problems with the ALDL bus because of BCM differences, fan strategy for low & high speed fans is different and fan wiring are also. Best to stick with a VS3 memcal in a VS3 and VT in a VT.
EDIT: VS3 memcal ran fine from factory, get it working first then worry about other changes, don't over complicate it at the start

[MAGP]

If the fan wiring is different wouldn't using a VT loom be a problem?

[yoda69]

Possibly.
VS3 ran the engine clutch fan and engaged the AC fan if things got hot.
VT ran the low speed fan by an ALDL request to the BCM and then high speed over ride via the ECU.
With out checking out the wiring diagrams not sure if the same pins are used.

Edit: VT also ran an AC pressure transducer and VS3 used a pressure switch, lot of subtle differences between them. If doing an engine conversion to something else VS3 can be easier to use than VT

[Whyzee]

It's better, but still not quite right. Still throwing the lean o2 sensor code, and when the CEL comes on, it leans out even more. I'll investigate that o2 sensor/wiring.

The way I see it, if you are going to the hassle of swapping over to the VT MAF style full sequential injection then you are best off getting both O2 sensors working so the PCM can control bank fueling to get the full gains otherwise you may as well just stick with the VS MAP based system.

The only reason I made the change was so that I could run sequential vapour injection. The injector drivers in the lpg ecu arent strong enough to fire all injectors at the same time. Otherwise I was happy with the map based system. If i can't get this sorted by the end of the week, I'll be reverting back to it.

I agree I'd fit both O2 sensors and swap over to a VT memcal. But he doesn't have a VT memcal and he has disconnected the 2nd O2 sensor so disconnecting the wiring from the PCM may help him in the immediate instance and may help others who do this swap in the future.

I had the VT memcal with no VATS prior to the current one - the CEL was constantly illuminated and the condenser fan was constantly running. Fitted the VS memcal and everything communicated as it should - and can now check for codes (which wasn't possible with the VT memcal).

If the fan wiring is different wouldn't using a VT loom be a problem?

The loom is VERY different where it plugs into the body loom (3 plugs near the brake booster vs 2 at the brake booster and one at the ECU for the VS). I'm confident that the wiring is correct (I didn't touch any of the engine management side of things apart from the oil pressure switch wiring as it's different)- I laid out the loom and traced each wire to each sensor and everything is wired as per the VS s3 diagram I found here on pcmhacking.

[Dylan]

No BCM would of caused the trouble on the VT memcal. Need to flag code 92 from memory low speed fan control it is.

[Whyzee]

I cut the wires for the extra o2 sensor as used for the VT. This seemed to make the first o2 sensor work properly.

I probed the wire signal wire for the remaining sensor and it showed approx .6v. Connected everything up again and went for a drive and did some more logging. For the first few minutes it ran better than it has for a while with the wideband showing the AFR's alternating between 14.6 to 15. BUT after that, I lost the o2 sensor and it leaned to 17:1 again cruising on the highway. Checked the voltage of the signal wire at the ECU again it didn't show any voltage at all...

O2 sensor voltage monitor:


I may have to run a separate wire to the sensor altogether to rule out wiring problems, I hope it's not an ECU issue

[yoda69]

It may have gone into lean cruise mode, look in your log at the target afr.
When 14.7 you get cros counts like you have, anything above this will show lean and no cross counts, can see in your image that afr is targeting 15.3 so looks like lean cruise is active. This is normal operation.

[Whyzee]

It may have gone into lean cruise mode, look in your log at the target afr.
When 14.7 you get cros counts like you have, anything above this will show lean and no cross counts, can see in your image that afr is targeting 15.3 so looks like lean cruise is active. This is normal operation.

Yeah, it's good up until 2.54. But the log goes for 5 minutes and after 2.54 there's no feedback from the sensor at all, even under load when lean cruise shouldn't be active. Strange how it runs so well then something goes haywire