another strange problem

[1990 300zx]

so today i realized my check engine light wasnt coming on when my key was in the on position. to try and fix it i disconnected the ecu for a while and put it back in. when i did that, i decided to check for any codes. it returned a code 55, so i figured it was fine, however i tried it again. this time i got a code 34. i did this over and over again, everytime it alternated between 55 and 34. any reasons why this would happen?

oh and it fixed the check engine light that wasnt coming on.

[t.mcginley.jr]

The check engine light not coming on isn't that unusual. Even if the ECU throws an error code it doesn't mean the light will come on. Mine has had 4 or 5 codes at one time and still not CEL came on.

Anyway, the code 34 is for your knock (detonation) sensor. They usually go bad with age, but more often then not its the little sub-harness that goes bad. It could just be corrosion on the connector or on the wires themselves, or loose wires or brittle connectors, etc. This is probably whats causing the intermittent code 34. Since your knock sensor is underneath the lower intake manifold (basically really hard to get to) its easier to buy another knock sensor and relocate it to the back on the intake, leaving the stock one where it is.

Read this: Knock sensor relocation

You can get OEM Nissan knock sensors on ebay for ~40-45 and an upgraded subharness from Z1motorsports for like $20-25

[nexus08]

The check engine light not coming on isn't that unusual. Even if the ECU throws an error code it doesn't mean the light will come on. Mine has had 4 or 5 codes at one time and still not CEL came on.

Anyway, the code 34 is for your knock (detonation) sensor. They usually go bad with age, but more often then not its the little sub-harness that goes bad. It could just be corrosion on the connector or on the wires themselves, or loose wires or brittle connectors, etc. This is probably whats causing the intermittent code 34. Since your knock sensor is underneath the lower intake manifold (basically really hard to get to) its easier to buy another knock sensor and relocate it to the back on the intake, leaving the stock one where it is.

Read this: Knock sensor relocation

You can get OEM Nissan knock sensors on ebay for ~40-45 and an upgraded subharness from Z1motorsports for like $20-25

That is a cool fix! Hadn't seen that yet. I'll have to remember that for when mine goes out (at the rate I'm going that should be next week!)

[1990 300zx]

okay, i was looking at my engine, and found this.
http://i974.photobucket.com/albums/ae22 ... 99d326.jpg

correct me if im wrong, but doesnt that has something to do with the knock sensor?
i've looked around and found nothing to plug it into. any help?
sorry about the wait for my reply, i've been very busy

[1990 300zx]

can anybody tell me w\if this is supposed to be plugged in somewhere, and how to fix it?

[nissanfreak12]

That is either for the knock sensor or VTC's. Very common for people to plug the knock harness in the VTC harness.