M35 Dtc Code 1805

[andy65b]

I have searched all the threads I could find looking for the meaning of the DTC 1805 (Diagnostic Trouble Code).

Eventually I found an obscure web page that told me what this fault was. 1805 = Brake Pedal position (BPP) switch - circuit malfunction.

So at last a meaning. Further reader said that the car showed this fault when the ECU has not seen the brake pedal signal in a WHILE! Very vague but this were the words I read.

Further reading of the G35 service manual said that the ECU put the car in a Limp mode with the following effects.

At Idle = no change

Under hard acceleration = reduced response

I am not sure I saw much change in acceleration but I did have slightly better economy. So perhaps the response was slower.

Now why did I get this code....

In the quest for the best performing M35 I could drive i have been very open to the idea of trying new things to realize the real power of the motor. Having done most mods to the car to improve breating of the motor, stopping and handling, we had been looking to find a way to improve throttle response off the line. The ECU is very intrusive in this area limiting throttle to 35% below 10kph.

Some smart M35 owners worked out that that the ECU reads the BPP and delays throttle response by approx 2 seconds when released. So the plan was to cut the input wire to the ECU.

The result was very good with 100% of throttle available whilst still on the brake pedal allowing very fast launch.

BUT the ECU once again outfoxed us throwing a CODE and limiting our fun.

SO the solution.... I installed a switch to the wire (as some other have done) and the fault code disappears on the next drive. I was also getting DTC code 0235 (turbo boost sensor circuit) but I think this may be how the ECU was limiting the FUN factor but as I have a Profec B installed I may have been outsmarting the ECU.

So now the Switch really should be labeled FUN as per Leon's suggestion.

Cheers

Andy

[scotty nm35]

So it finally threw a code. Looks like a switch is the answer.

Did it cut the throttle though? I don't care if the light comes on...

[andy65b]

So it finally threw a code. Looks like a switch is the answer.

Did it cut the throttle though? I don't care if the light comes on...

I didn't notice a significant change but the car was running a little more economically.

When it threw the 1805 code it also threw the 0235 code (turbo boost circuit) so I suspect it was trying to limit boost. But as I have the Profec B fitted I think it was unable to limit boost :banana:thus the 0235 code.

[Commsman]

So it finally threw a code. Looks like a switch is the answer.

How come Andy's car throws a code & others haven't as yet? Has he just travelled more km's, stopped/started more often or done something else to trigger the ECU into realising it hasn't seen the brake on for a "while"....

I love how our cars behave so differently. M35's are always keeping at least one of us thinking/guessing. There's nothing boring about our rides

[scotty nm35]

I wouldn't know if it threw a code, my light has been on since the emanage went in. As long as it doesn't lean out the engine too much on boost I guess. Have you done any long drives Andy?

[andy65b]

Each day I commute about 40km each way to work. That was the longest trip done in that time.

[Daleo]

With the switch situation;

Would it be possible to set up a Momentary type switch, with a delay board (i.e. Jaycar window delay, or similar for example) to break the BPP connection for say; 1 minute, then automatically re-engage, once the delay is finished?

That way when you wish to do a full throttle start; you push a Momentary switch to disengage the BPP circuit, and after a minute; (or 5 minutes, or 10 minutes; whatever) then you don't need to worry about flicking the switch back later.

Not really my area of expertise; but it might stop inadvertent loss of performance just because you forget to flick the toggle switch back.

[Commsman]

Ahh, so Scotty's could have been on as well, just masked by other MILs. What about Aaron? No light yet? I haven't gone more than maybe 80kms since I did the mod, but have switched it out/in a few times & hence keeping me error free.

[Commsman]

Would it be possible to set up a Momentary type switch, with a delay board (i.e. Jaycar window delay, or similar for example) to break the BPP connection for say; 1 minute, then automatically re-engage, once the delay is finished?

Sure, that wouldn't be very difficult, but I reckon if you were planning on driving hard it would be easier to flick a switch which leaves you ready for action the whole time. Then just turn it off when finished. If you forget (for the next week ), the worst that will happen is a trouble light on the dash which is fixed by returning the switch to normal & a restart.

[Daleo]

Sure, that wouldn't be very difficult, but I reckon if you were planning on driving hard it would be easier to flick a switch which leaves you ready for action the whole time. Then just turn it off when finished. If you forget (for the next week ), the worst that will happen is a trouble light on the dash which is fixed by returning the switch to normal & a restart.

Ahh ok, I thought you needed to do a MIL reset; if all you have to do is turn the key off it's not a big deal.

[Sunkist]

im in the same boat as scott wouldnt know due to the emanage..

maybe im due for a jaycar visit.. lol

[Jetwreck]

im in the same boat as scott wouldnt know due to the emanage..

maybe im due for a jaycar visit.. lol

same boat.........just bought a momentary switch though as it only needs a 1 connection every couple of hundred with the brake on.

[Sunkist]

are we sure thats all thats needed? the car being this smart i wouldnt be suprised if it detects a faulty connection thinking it comes on momentarily..

does the engine light dissapear as soon as it notices a connection?(for those without emanage)

[andy65b]

does the engine light dissapear as soon as it notices a connection?(for those without emanage)

Yes, it does.

[scotty nm35]

Just another code to add to the list...

At least it doesnt go into full limp mode.

[zei20l]

dont forget Andy has an impul ECU. it may have some G35 fault codes built into it or something?

anyway ill cut mine soon and see if it comes up after a few weeks

[andy65b]

installed a momentary switch on Jetwrecks car today and he checked his fault codes and he had the 1805 code.

[scotty nm35]

There are many M35's getting around with the mod done now, none of the ones down here have the MIL up yet that I know of... Perhaps its just you Canadians?

Im sure they will pop up eventually. I fitted a switch in one today, just next to the ecu. If the light comes on he will just switch it back on for a minute. We need to come up with a simple switch/circuit to automatically enable the brake circuit for a single pulse. Perhaps a momentary switch on the brake or handbrake?

[zei20l]

or something that only allows the brake signal to be turned on for 1 min after first starting the engine

[andy65b]

There are many M35's getting around with the mod done now, none of the ones down here have the MIL up yet that I know of... Perhaps its just you Canadians?

Im sure they will pop up eventually. I fitted a switch in one today, just next to the ecu. If the light comes on he will just switch it back on for a minute. We need to come up with a simple switch/circuit to automatically enable the brake circuit for a single pulse. Perhaps a momentary switch on the brake or handbrake?

Maybe connect the momentary switch to the park brake.

You always have you foot on the brake when you release the park brake.