Hi all,

 

A quick question I hope.

 

I've been searching the forums about problem my Z picked up at weekend, and from what you all say it would seem to most likely be the PTU. (Car runs for 15 mins, stops, cools down - repeat at will !).

As suggested I ran the ECU diagnostic to look for code 21, this I duely got. But I also got the code 34 'Detonation Sensor Circuit'.

 

My question is, are these two likely to be releated, or just coincidence that I have both. ?

 

I should probably mention here that for a couple of weeks I seem to be running without turbos (only goes up to 0 on gauge, is this running in safe mode/safety boost ?). From reading lots of posts about the detonation sensor, this could be the reason andtherefore not related to the PTU stuff....

 

Thanks for any help advice

Ash

Hello Ash,

 

It's just coincidense that you've got both errors, they're not linked to each other.

 

I'm afraid zero boost tends to be a siezed turbo. When you're in safety boost, you still get 7 psi. You will be running in safety boost as your det sensor circuit error will cause this but as I said you should still have 7 psi :(

 

Vijay

Hey Ash,

 

1) Nip to halfords (or similar) and get some di-electric grease (£1.49) usually in the spark plugs section - this is rated to ~200deg C

 

2) 'Borrow' an emery board (fingernail file) from the missus

 

3) Disconnect the battery -'ve lead for half an hour

 

4) Whilst waiting open the bonnet and locate PTU and carefully unplug connectors on both sides, then remove.

 

5) Once out check for corrosion on PTU contact pins - if not shiney coppery colour gently clean using emery board until they are.

 

6) Check PTU connector plugs for oxidation (greenish tinge) using a small screwdriver to gently scrape it off if corroded, put liberal coating of dielectric grease on PTU connector wiring harness and install unit back in car.

 

7) Unplug Det. Sensor harness and check for corrosion at each end of the plug, cleaning where necessary and grease it up (also may be worth checking with a multimeter to see if resistance is within specs - if you don't have a multimeter skip this step for now)

 

8) Hopefully your 30mins should have flown by and reconnect the battery -'ve. Before starting the car check the ECU for codes - don't be surprised if it comes back as 55 (all clear!)

 

9) Warm her up to normal operational temp + take her for a spin round the block and test the diags again and let us know what happens....

 

Useful links:

 

 

Detonation/Knock Sensor Location and Tests

 

What does the PTU look like?

 

Good luck m8y!

Cheers Nibbler,

 

I tried the steps suggested for the PTU, replaced it all and tried again. Unfortunately I'm just getting the same symptoms, stopping after 15mins, and the same codes on the ECU.

 

Does this mean it's definitely the PTU ? Replacing the only sensible next step, or is it worth trying out a different one to check first. in case it's something else ?.... anyone know where I could get hold of one to try(I presume Nissan wouldn't be too helpful !!).

 

I still getting the detonation sensor code, so would it be best to investigate whether I have detonation? Knowing nothing about this (except what I'm trying to read on the site), is this likely to be a major problem or more likely just the sensor circuit?

 

As an aside, how many miles is generally considered lifetime for the 300's, I'm currently up to 165,000 on a 91 model. Just wondering if major outlay is going to end up sensible or not...

 

Thanks for any help/suggestions

Ash

the PTU fails internally - theres a "fix" on andyp's site which worked for me.

 

basically you cut open the rear of the PTU, on mine, 1 of the contacts had broken causing it to cut out when warm & the contacts expand.

 

i soldered a wire in its place which cured it for me. I still replaced it with the new modified type from Courtesy Nissan, but it got me by for a week :)

 

code 34 means theres a fault in the det sensor circuit - not that your getting detonation. it puts you in safety boost as it has no way of detecting whether you do have detonation or not.

 

you can check the circuit out with the resistor "fix", but wouldnt leave it in as the ECU still has no way of detecting detonation & will still run at full boost/advance

PTU fix

 

Det sensor BYPASS

 

:)

I should probably mention here that for a couple of weeks I seem to be running without turbos (only goes up to 0 on gauge, is this running in safe mode/safety boost ?). From reading lots of posts about the detonation sensor, this could be the reason andtherefore not related to the PTU stuff....

 

But does he not have more serious problems?

 

Vijay

Originally posted by vijay

But does he not have more serious problems?

 

Vijay

 

is it really running without any power??? could just be a dodgy gauge/sender

 

or you could have more serious problems :(

Maybe the vac pipe has fallen off the sender ... It should be pretty obvious if he was really running at 0psi !

 

 

Originally posted by Paul C

is it really running without any power??? could just be a dodgy gauge/sender

 

or you could have more serious problems :(

True - but he does say it "only goes up to 0psi" - which implies it's starting off much lower.. Still, could be the guage, but that would rule out the vac pipe.

 

Still, the cutting out sounds like PTU to me (like others have said), and the code 34 is the classic det sensor that every Z seems to have.

If you do end up needing a PTU, I can get hold of a brand new series 2 one for £150.

 

Vijay

Yeah, good point, I was thinking of my setup where I have two gauges and the pipe fell off one end of the t-piece.

 

 

Originally posted by aaronjb

True - but he does say it "only goes up to 0psi" - which implies it's starting off much lower.. Still, could be the guage, but that would rule out the vac pipe.

 

Still, the cutting out sounds like PTU to me (like others have said), and the code 34 is the classic det sensor that every Z seems to have.

You can actually pipe up the boost guage so it only reads up to 0psi lol. You just get all the vac piping ****ed up :D How hard does the car pull? I've had a seized turbo and the car was soooooo slow. No speed problems but very very slow getting there.

 

PTU needs replacing - the ecu and the symptoms are telling you that.

 

Det sensor circuit - please please do not drive round with the resistor 'fix' as you will be seriously risking damaging your engine. The det sensor doesn't work over 3500rpm so won't pick up detonation on boost (which is where it really needs to). It is more of a protection against bad fuel etc where you will get det very low down the rev range - the ecu can then put itself into safety boost to protect the engine throughout the rev range. This sensor is important - make sure it works!

 

HTH

 

CheerZ,

 

Andy

Thanks for all that.

 

I think I definitely have knackered turbos, gauge just goes up to '0', and car pulls like a complete tank. Ok once it got some speed up though.

 

Looks like def a new PTU !!

 

Now for a stupid question, what exactly is detonation ? If my sensor is buggered, then presumably it doesn't necessarily mean I am getting detonation....

How do I tell ? (onviously this will be once I get the car going for more than 10 minutes..)

 

Vijay I may take you up on that offer, when I get time to sort things out.