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Code 26

huddy

By huddy,
in Engines & Forced Induction

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huddy Veteran

huddy

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Posted (edited)

I had the engine light come recently on in my S2 RB25DET NEO stagea, It is completely standard with the exception of the standard high boost mode which was done almost 3 years ago.

i had a engine diagnosis done and it's shown to be: Code 26: Boost Pressure Sensor.

Ecu was reset but still no fix.

I've done some reading and found:

"NEO has a "Boost Pressure Sensor" aka map sensor on the back of the engine rocker covers."

"Code 26

Boost Pressure sensor (Turbo models)

The boost pressure sensor is open or shorted (abnormally high or low voltage is registered).

Check harness and connector, check for boost pressure leaks, check boost pressure sensor"

I've removed the sensor and had a look at the small filter inbetween it and the J pipe and it doesn't seem dirty or blocked. I was wondering if i am looking at the correct sensor and it sounds like it is actually sensor related? or possibly a pressure leak somewhere?

I looked at the connector and it is clean and the wiring looks to be unbroken.

The car still runs perfectly (well appears to) and from this error code coming on, shown no actual sign of change in idle/drive/performance - The only thing that brought it to my attention was the light...

It does not R&R and it does not misfire.

The sensor is a small one located on a metal bracket off the firewall (situated above about #6 cylinder/coilpack)

It is a small black box about 5cm long by about 3 cm wide - with 2 x 10mm bolts screwing it to the bracket. Underneath it has a small vacuum hose which goes to a very small air filter (about the diameter of a 10 cent coin and about 1cm thick) and then a little more vacuum hose and then attaches to the standard intercooler piping just after the throttle body.

It read on the top:

"PS66-01

9X19

HITACHI

BOOST SENSOR"

Any help would be greatly appreciated in fixing this problem and making the engine light go away. :P

Cheers

-Matt

Edited by huddy
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Beer Baron Grand Master

Beer Baron

Posted
Posted

afaik, there is only 1. it's for the gauge. the ecu goes not need a boost pressure sensor. it uses afm to measure air flow, not manifold pressure. no idea where you got 4 sensors from. if they needed boost pressure for 4 things they still only need 1 sensor....

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STATUS Grand Master

STATUS

Posted
Posted

huddy anything over 18psi (ish) brings up this CEL

There is only one boost sensor and it is used for fuelling and boost cut etc, becareful what you do with it as it is integral to the mapping, if you plug it to stop the overboost CEL it will lean out 1 whole A/F which can lead to issues obviously.

if you want to have a chat drop me an email with the exact issue or cal me at the shop 2moro before 12 (leave a message if it rings out as i'll be on the dyno)

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huddy Veteran

huddy

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Hey Trent, cheers for the reply, however i've only just read it and i'll update my findings...

I read a R34 workshop manual to try diagnose the wiring pinout - and possible causes and fixes for this code. I read that this sensor rely's on 2.7V and the engine light will come on if it is short circuiting (if it is below 0.6V) or if it is an open circuit (above 4.8 volts). I ran a multimeter on it and jiggled a couple of wires and to my surprise - engine light is now off - BUT - i know have a very very minor misfire, it only occurs at low RPM with no boost (only very slight throttle) AND it is not a constant issue (also there is NO engine light on now)... So back to the research board again to try and find the solution to this problem....

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  • 1 month later...
Flargh! Enthusiast

Flargh!

Posted
Posted
Hey Trent, cheers for the reply, however i've only just read it and i'll update my findings...

I read a R34 workshop manual to try diagnose the wiring pinout - and possible causes and fixes for this code. I read that this sensor rely's on 2.7V and the engine light will come on if it is short circuiting (if it is below 0.6V) or if it is an open circuit (above 4.8 volts). I ran a multimeter on it and jiggled a couple of wires and to my surprise - engine light is now off - BUT - i know have a very very minor misfire, it only occurs at low RPM with no boost (only very slight throttle) AND it is not a constant issue (also there is NO engine light on now)... So back to the research board again to try and find the solution to this problem....

Hey huddy, did you solve this problem. My R34 GTT has just started suffering low boost, like 3psi max :) and after running the diagnostic i got the code 26 error. Since it's a boost related error and i'm getting almost no boost i'm wondering if it's related.

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huddy Veteran

huddy

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Hey guys

I didn't have a loss of boost so perhaps yours is actually a faulty sensor. I'd start with that anyway...

As for the manual I googled to find it on a us forum, I think it was Nico club or something

I did fix my problem, it was a bad contact causing a voltage problem causingthe code

cheers

Matt

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Haines Rising Star

Haines

Posted
Posted

ahhh the good old 18psi gauge

How did you get your car to trip that light before the actual Boost cut came in

From memory mine used to hit hard around 14 psi

also Trent have you played around with the TP limits in nistune regarding the Boost cut I wanna set mine to cut at 19psi as a safety if it goes over 18psi

or is it going to be a trial and error sort of thing where I keep adjusting the cut until its right

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Flargh! Enthusiast

Flargh!

Posted
Posted
Hey guys

I didn't have a loss of boost so perhaps yours is actually a faulty sensor. I'd start with that anyway...

As for the manual I googled to find it on a us forum, I think it was Nico club or something

I did fix my problem, it was a bad contact causing a voltage problem causingthe code

cheers

Matt

Just out of interest, where was the bad contact? Mines reading 6V

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huddy Veteran

huddy

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Just out of interest, where was the bad contact? Mines reading 6V

it was on the connector for the boost pressure sensor.

From what I can remember from the workshop manual, the error light and code comes on from either not enough voltage (under 2.6 I think makes closed circuit) or too much voltage (over 4.7 I think is open circuit). Correct voltage needs to be between these... I think the manual says around 4.2v...

Hope this helps... It's definitely a painful problem...

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  • 3 months later...
lowbro Community Regular

lowbro

Posted
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it was on the connector for the boost pressure sensor.

From what I can remember from the workshop manual, the error light and code comes on from either not enough voltage (under 2.6 I think makes closed circuit) or too much voltage (over 4.7 I think is open circuit). Correct voltage needs to be between these... I think the manual says around 4.2v...

Hope this helps... It's definitely a painful problem...

Hey Huddy,

I also have code 26 along with TPS problems and a high cold start idle in another topic with my R34 NEO6 which is driving me nuts. I don't want to have to start opening up the loom and start performing circuit tests on everything, and I believe I have high voltage on the BS also.

But when you say it was the connector (Boost Sensor Connector Plug?), did you clean the contact pins with contact cleaner and this resolved your closed/open circuit issue or did you do something else?

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