Odd problem w/knock sensor

[bwh13]

S52 swap OBD1 with all new sensors with 540 MAF, 413 red label with TRM chip. Been driving the car since October with no issues, passed AZ dyno-run emissions test easily a couple months back.

3 weeks ago I had the vanos unit changed for a Dr Vanos kit. Upon driving home the MIL comes on, code says it's the rear knock sensor.

Checked the wiring, switched the wires between front and rear sensors to see if it was the sensor.

Finally decided to swap ECU's (have extra stock 413 red label), and the MIL goes away. Put back in the TRM chipped ECU, MIL comes back on. Swapped the TRM chip into the extra ECU, MIL comes on.

The only common factor seems to be the TRM chip. I'm guessing the knock sensor function must be part of the EPROM programming on the chip, since changing the chip to the stock one fixes the MIL....

Has anyone run into this before?

[Uber E30]

They are good guys, im sure if you send it back they can reflash it. Something might have just got messed up in the memory.

[jrdeamicis]

You should re-time the vanos. With the new chip the ignition timing is more aggressive and sensitive to changes in the cam timing.

Start there.

[bwh13]

Wouldn't the shop do that when installing the new unit? I also had the upper chain tensioner replaced, so that would require the cams be re-timed.

[jrdeamicis]

Well there it is, you have to remove the secondary chain to replace that tensioner.

Im sure the timing is a TICK off. Does it have a little lumpy idle?

[bwh13]

I would think they had to use the cam holding tools, etc to get the vanos unit and sprockets all lined up properly before re-assembly.

What else would need to be done? What do you mean by re-timing the vanos?

[jrdeamicis]

You can get it all to line up with out the tools. Are you sure they have the tools?

Just make sure the timing is perfect. Also it could be dealing with the CPS or Crank position sensor. If you are running an aggressive chip + low octane / crap fuel. Problems can be had.

[bwh13]

I'm sure they have the tools it's a BMW only shop.

I have added octane booster as well just to eliminate that variable.

All new sensors so that should eliminate thosevariables as well.

It's perplexing that the stock DME doesn't activate the CEL while the aftermarket chip does, plus why would only the rear knock sensor code come up and not both of them?

I didn't think there was anyway to change the timing as the DME controls that; it's not like having a distributor that you can advance/retard the timing...

I'll have to listen to the idle to see if it is lumpy, didn't seem that way last time I started it up...

OK idle isn't lumpy, 900 rpm with chipped DME, 700 with stock DME. No CEL with stock DME, drove it around for 10 minutes. With chipped DME CEL comes on just revving engine to 2000...

[jrdeamicis]

Just as an example my Crank position sensor had died. But it wasnt throwing a CEL. It would throw a Rear Knock sensor 4-6.

It would drive fine until 3k then pull ignition timing. It didnt throw that code because I was missing a single ground between the coil packs and valve cover.

I am not saying that your CPS is dead, its just an example that sometimes the symptons are not very clear. Also they could have damaged the sensors while they were in there by accident. Both crank and cam. The trigger wheel only has one way to go on so its not that.

Or it can have NOTHING to do with the vanos.

[Apex381]

Don't know if its related, but I just put in a TRM chip and I have the same problem. Its throwing a knock sensor code when there was no problem with the stock chip. I'm going to email Matt again about this and see what he thinks.

[jrdeamicis]

Rut oh.

[rneedham1979]

I am getting the same knock sensor code with an occasional CEL. I thought it was bad gas or to aggressive time but my buddy put 110 is it and it is experiencing the same thing.

Hopefully it is the my knock sensor.

Ryan

[matt]

Send me an email if you guys are still having issues.

Matt@racersmarket.net