Site hosted by Build your free website today!
How to get rid of a dreaded code 34 (faulty detonation sensor) by relocating a new detonation sensor in the VG30DE(TT) engine
90+ Nissan 300 ZX [Z32] Twin turbo or NA.

By Henri Le Hir

My Z are a 1990 (AUTO) and a 1992 (MANUAL, "Continental European" Nissan 300 ZX Twin Turbo, 2+2 (!!) (left hand drive). All the tests have been done on these cars.

Hopefully, the following "How-To" applies to all the Z32 all over the world.

4 years ago (damm, I'm getting old), I had a problem with a failing detonation sensor, bypassed it, and wrote a "How-To" about it.

Go there first if you don't know what is a code 34, how to diagnose your detonation sensor, and if bypassing it would solve your problem.

However, I never was actually completely satisfied about my "temporary" fix that turned out to be a quite permanent one.

Of course, the Nissan Official way is to remove the upper and lower plenum, remove the old & damaged detonation sensor & sub harness, and re-assemble the engine. As you might imagine, it takes quite some time, and thus is costly (often quoted in the vincinity of US$1000).

Alternatively, you can drop the gearbox, and from under the car, if you have the right tools, and very tiny hands, you can manage to reach the detonation sensor, unscrew it, replace it, and re-screw it in's akward, and not easy.

So, finaly, I decided to find an aternate solution to this problem that would work for me.

After a lot of thinking, looking around in the engine bay, reading the Z32 manual(s), discussing with other Z-Nut (thank you for your time, friend-Z), I finally found and implemented the following....Hope it'll help you.

First of all, a couple definitions.

To clarify this, in the pictures, I put a blue/red arrow pointing to the FRONT of the engine/car.

For the following, you will obviously need a detonation sensor, and a detonation sensor sub-harness.
AFAIK, for the Z32-TT (please DBL check for the NA engine), part numbers are

You can either manage to get both of them from a damaged Z (from an individual in the Classifieds of , from a Junkyard like Autogator), or new from an on-line auto-parts supplier like Courtesy Nissan (with a 25% discount on Nissan Stock parts for TwinTurbo.Net Members)

Let's start !!!

Locate the area

This is the area where the new detonation sensor will be installed.
Just by the detonation sensor connector.

If you have a close look in there, you will see the hexagonal heads of two bolts / studs, just in front of the detonation sensor connector. I decided to use the left one because it was easier to put the detonation sensor here (in my LHD). In case you have a RHD Z, it MIGHT be possible that the right one might be the one to use, as some parts in the RHD engine are reversed, but I'm not 100% positive, you've got to be creative.

Now, unplug the connector.

Start to work

Remove the left bolt with a ratchet (and a 12mm socket), and have a look at it (it's the upper one in the picture).

The thread pattern are M10 (Metric 10)
The depth of the stud is 75mm (that is, NOT counting the head)
The 2 captive washers are metallic, and are 3mm thick (both of them together)

This bolt directly screws into the engine, and I figured that if detonation would occur....

However, I completely understand that the BEST possible location for a detonation sensor is where the Nissan engineers put it....right in the middle of the engine. I feel this alternate location is acceptable, but if you're not comfortable with it, go with Nissan and have the detonation sensor properly replaced.

I decided to replace this bolt with a longer one, that would be long enough to accept the detonation sensor on top of the block.

The detonation sensor is 20mm high

Unfortunately, I could NOT find a M10 bolt that would be long enough to do that, so I bought the following

Using an electrical metal saw, the M10 threaded rod was cut according to the following : Given that I wanted to be able to REMOVE that "home made" bolt, I cut a slit on one side, making it easy to install / remove with a flat head screwdriver. You may decide to do it or not, your call, but if you don't, and you have to remove the bolt, you'll be in trouble.

It's VERY important to deburr your home made bolt (bolt is steel, block is aluminium), and check that its threads are NOT damaged.

In order to have a working detonation sensor, it's MANDATORY to have a good electrical connection though the BASE of the detonation sensor.
To achieve that, do the following

This is the final result, no more code 34, no more safety boost, and hopefully still some good protection against low RPM detonation (after 3500 rpm, it's anyway not detected by the ECU)

PS : I couln NOT find the torque value for the stock bolt / stud, if you have it, let me know.

The above assembly allowed me to successfully get rid of the code34, and survived more than 100 temp cycles in one month, without any hiccup.

Alternate Method (not using the M10 Safety Eye Bolt) (thanks Roy for the idea)

Zee you

Written by H. Le Hir / 2002.04.10@22:55 email