New det sensor and new sub harness but still code 34

After running the "temporary" 2 year band aid resistor trick to fool the ECU to think that no code 34 exists I finally went out and bought a new sensor (aftermarket) and sub harness.

The problem is after an install (relocated on top of plenum - rear drivers side bolt) I'm getting a code 34. The entire wiring loom in my Z is only 3 months old. Tried looking it up but found nothing. Is there a way to test the new detonation sensor?

I'm getting detonation during hot days (no vac leaks, tried different AFMs, ECUs, new wiring loom, new IACV and all deletes including EGR done. Timing is also set to 15 degrees. Detonation thankfully doesn't occur when code 34 is present. So my next attempt is to get a detonation sensor up and running.

 

Items like det sensors always buy genuine imo.

If you're wiring is good (easy to test) than it's a faulty or incompatible sensor.

 

Yep definitely... I did the same. The one time I bought an aftermarket part it bloody doesn't work

Buying OEM DET and harness soon... But have the bandaid in for now.


Plus I don't trust that relocation trick. It's either bypass or origonal location IMO

 

"After running the "temporary" 2 year band aid resistor trick to fool the ECU to think that no code 34 exists I finally went out and bought a new sensor (aftermarket) and sub harness." - Did this work & trick the ECU? If so, it would indicate the wiring & connections from the sub harness to the ECU is serviceable.
"The problem is after an install (relocated on top of plenum - rear drivers side bolt) I'm getting a code 34. The entire wiring loom in my Z is only 3 months old. Tried looking it up but found nothing. Is there a way to test the new detonation sensor?"
The problem is either the detonation sensor, the harness, or the connections.
The sub harness can be tested with a multimeter, or try reinstalling the resistor both before the sub harness & then again where the detonation sensor connects.
Yes, the detonation sensor can be tested.

 

Yes, it is definitely the aftermarket sensor. Code 34 disappears with resistor connected to sub harness itself. Time to send it back to its seller, get refund and go OEM. Thank you guys for all your help.

Also, does anyone know how much timing the code 34 cuts out or does it just run richer fuel maps? I may as well set the CAS a few degrees back to quieten down the detonation itself.

 

I'd still be looking for the cause of the detonation in the first place. Detonation is not the norm and even though the ECU compensates (when the Det sensor tells it to), you should still try and fix it.

It looks like you have been onto most things. Just our of interest, have you tried a bottle of the octane booster stuff (the expensive type) to see if you just have bad fuel?

Otherwise, how are engine temps on these hot days when it is pinging?

 

He said he's getting detonation.

 

killed mine as well, bypassed it ran good then backed right off timing into limp mode, I am surprised you are not getting limp mode after code 34 appears

 

Are you saying you got code 34 after bypassing?

 

Thanks for the reply guys!

So a simple run down;
- Bypass in place (no code 34) = PING PING
- No bypass (active code 34 ~ limp mode) = no pinging

As the original post said, I have tried everything to lessen the detonation. I always run BP 98 ultimate. Turned back the timing on Saturday just by hand and so far no det during hot days. Marked it so I can turn it back to normal when the weather gets cooler.

 

Was the CAS in the middle of slots before you adjusted it? I recently had an issue where my timing light was giving a false indication of the ignition timing. To make sure you need to get a silicon lead adaptor for the coil pack so essentially your coil pack is connected to the plug via a silicon lead and the coil is sitting on the upper plenum, then put the inductive pickup around the silicon lead.

Also what heat range plugs are you running? How much Boost are you running? Is your motor stock? Has the ECU chip been modified?

 

I have new OEM lead and sensor. Sometimes the fault appears out of the blue and consistently. I wiggle the plug a little and it goes away for a while.

I will get around to replacing the old corroded plug one day.

 

Yes, but here's a question: If the sensor detects detonation and the ECU throws the engine into safety mode, does the ECU also raise a code 34? It's all done by monitoring the current down a single wire to the sensor, so can the ECU distinguish between a wiring fault and detonation?

 

The engine goes into the low octane map (reduced timing and increased fuelling) to protect the engine if sufficient detonation is detected within the defined area of the timing map. There is then a time delay the ECU waits for until it returns the ECU to the High Octane map providing no more detonation is detected.

 

Code 34 is a fault with the sensor or sensor wiring

taken from page EF & EC -51 from the manual as stated before. Quote

34 Detonation sensor circuit ? The detonation circuit is 0pen or shorted. (An abnormally high or low voltage is entered.) ? Check Harness and connector
? Check Detonation sensor

Logically if the resistor bypass gets rid of the code 34 then the wiring and the ECU are OK. The Sensor must be giving the wrong output voltage to the ECU hence the Code 34. Borrow a genuine or working sensor and see if the code is removed.


MichaelZ

 

Fantastic, it is really good to now know how the ECU responds to detonation. I knew timing was reduced but didn't know the fuel maps were also increased.

Funny observation. When I clear the self learn mode there is no detonation. Over time, the detonation starts again. This is on normal fuel maps - code 55. I know the temperature sensor is vital and if not functioning right will cause issues to mixtures but mine was replaced not long ago. I'm aiming more towards the TPS as partially not doing its job correctly due to inconsistent gear changes sometimes. Maybe this will have some effect on air / fuel mixtures and firing points?

 

what variation is your car? NA/TT, Man/Auto. Personal experience has proven that shifts are better on an NA Auto with TPS set to 0.42V

Also recently had a bit of a play with timing on my NA. Was advanced to 18-degrees and experiencing slight detonation when running anything under 98octane. Retarded back to 15-degrees and most recently, following the underbonnet sticker, 10-degrees ('93 Series2 NA). Car is a obviously a little less responsive, but no detonation whatsoever with 95octane.

As Karl suggested, be a little wary of induction test lights when picking up at the coilpack plug. Opening and closing the clamp can result in timing display differences of over 5-degrees. Best to get a spare coilpack and a silicone plug lead, fit the lead to the coilpack stalk and use induction clamp around the silicone lead.

 

Car is an NA auto. jspec ECU with no chips. Someone else was telling me 0.42v works much more effectively also with an auto. I will try that.

Motor is also stock with NGK PFR6G-11. Cylinder 6 has less compression than the rest I am guessing from previous overheating with the previous owner but the cylinder still fires fine. I was told the NGK plugs did not need gaping for an NA application.

When I last did timing, I had the coil pack sitting on top of plenum with a silicone plug lead running between cylinder 1s spark plug and the coil pack. Was sitting right on 15 degrees BTDC.

On Saturday I moved the CAS to the left by hand to lessen detonation. Power has been compromised but it has lessened detonation a bit.

Still at a loss, I know car engines can detonate over time but there is something majorly contributing here that I am clearly missing. My theory is too much air. Probably something around the intake piping under the front bar.