C4 EGS Gear Selector Coherence Fault

[AlienC4]

I guess it must be relatively straight forward to get the selector cover off ? I'll take a look tomorrow

[GiveMeABreak]

I guess it must be relatively straight forward to get the selector cover off ? I'll take a look tomorrow

If you want the Diagrams for the removal and fitting, just send me your VIN and an email address via Private Message.

[AlienC4]

Thanks just sent

[GiveMeABreak]

Nothing received as yet, did you click on my avatar and then click the 'send private message' link?

[Cancel]

Hi everyone, just browsed the forum for this error message..
Had the same issue last week, went to Citroën and the guys changed the brake switch, took 15 minutes or so..
Now it's all good and back to normal.
@ Alienc4: have you changed yours? Did it made any difference?

[OctavianR]

That code is: P1704 Brake switch signal : Consistency between 2 brake signals. I don't have one of these systems, so can't comment further - but would be tempted to look at the brake switch as a possibility? There are a few C4 owners who may have more info if you hang on for a bit.

Hello. Firstly, my problem begun as an ABS ESP faults mid drive (driving along minding my own business). I said to myself that it is nothing and probably same abs sensor on a back weal is touching the rubber magnetic strip. But it got worse, i,ve noticed that standing on a slope at traffic lights the brake that holds the car in position while you take the foot of the brake was disabled and the car will begin slipping away backwards. Had to keep the left foot on the brake and to slightly accelerate, in order not to hit someone. Right, and 4 days later, it happened, i was in an underground parking looking for a spot to leave the thing (ABS ESP errs were on). while backing up approaching a wall i could see in the mirror that the stop lights were flashing frenetically while with the foot on the brake firmly, and after the flashing..it would suddenly go dark(turning off, but the car was still on, and foot on the brake).
I parked and something told me to start the car again,..but...nothing it was a NO CRANK situation, although the electric system was on, with all the check lights. I.ve panicked, looked at the selector it was into N, but still the brake symbol was flashing like if it was on A or R, or....Brake pedal not pressed (which it was). Panicked some more, as it was Sunday, and no one would tow me away, no one would have even entered inside the parking lot as it was too low for special rigs.
So, approached the issue thinking of it was a computer.Turn of battery!, disconnected the battery, waited for...seconds, reconnected it, tried again, nothing. Ok, i,ve pressed the brake pedal as hard as i could, and very rapidly turned the key in the ignition not waiting for the regular steps...it worked!, managed to start it!! took her home, left it for two weeks on the drive way, decided to take her for a spin one Sunday, brought her back, left it in the drive again and that was it, IT WAS ALL THAT SHE WROTE. 2 weeks later same thing, power on, but no start situation. Moreover, the white light on the back was on, although the leaver was in N, and could not for the life of me, even push it(the car down the slope). It was like the ESG gear system transformed itself into a regular automatic system. So, yeah, i was dealing with a dead weight. Left it for a week, and searched all the symptoms on google. most of them were indicating the brake light switch, being the cause, which seemed ok, because at the tie my stop lights were completely dead. But what,s up with the R light going on in the back when the key is into contact? and it being stuck apparently into gear?
Took a lip of faith, and bought myself a new BRAKE LIGHT SWITCH most expensive one they,ve got (5.97 GBP). Cycled to the place with the busted original one in my hand, and thought to myself..i,m (-expletive removed-) if this does not work. Got back, cycling gear still on me, bike next to me, plugged the thing back in, after re-mounting the old one back again to see how it should go in, and not the screw up the new one, which looked crappy, and of poor quality. put the key into ignition, same pedal warning, still not working. pushed the pedal for one last time but this one time more firmly, and a click inside the engine bay sounded(metallic click), brake symbol off, aaand it worked. BRAKE LIGHT SWITCH CAN (-expletive removed-) UP YOUR CAR, IF IT,S A CITROEN THAT IS. TOOK her for a 15mile run, shifted good(normally), stop lights , all on, when it needed to be. But when i took the OBD READER out to read it, just for the fun of it, it showed up, the most terrifying err code (for me) ever. P1704 which apparently is a faulty gear box. (to be honest, it says gearbox faulty for other brands, my OBD 2, is a cheap on off the INTERNET and when it reads codes, apparently it does for the most known brands (citroen not included).So after seeing your answer regarding this error which haunted me, for the last hour, it downed on me that this was it: error code: P1704 IS for and related to the brake light switch.

SORRY FOR THE LONG POST, HERE,S AN IMAGINARY POTATO.

hope it helps someone out there, cause it was a real mental struggle for me.

[ekjdm14]

Yummy potato, I can fry that up in our fuel

Interesting thread to read, these EGS systems are starting to interest me more & more.

[AlienC4]

Hey Guys,

some useful information from AlienC4 the guy who opened this thread.
I never bothered getting this problem fixed, instead I found a solution which works every time and doubles up as a theft deterrent.
I discovered that if you press and hold the footbrake you can select your gear position (R, N. A, M)
then use your paddles to toggle between the options which show up on your car display panel.
On my car, the 'R' select works anyway.

So if you are in 'R' (reverse) and you need to get into 'N' to start up here's what you'd do:
1, turn on ignition to light up dash.
2, flick the selector to 'N'.
3, may show up "gearbox faulty" message at this point (if it just goes to 'N' as it should then the fault has temporarily ceased).
4, if the display stays in 'R' then press & hold the footbrake.
5, pull towards you (once) the right steering wheel paddle, this will change the 'R' to 'N'.
6, start the car.
7, Once started, with your foot on the brake, select A1 on the selector and flip the right paddle once to toggle to A1.
8. GO !

BTW
a few interesting observations:
1, Although you may find that the 'M' selection doesn't work with this fault, you can still use your paddles and normal if you want to switch up or down a gear while driving
2, While this fault is manifesting, the cruise control does not work.
3, It's probably close to a year that I've been using the above system rather than completing the repair, works every time and doesn't get worse.

Problem solved.
All the best, AlienC4

[lionfight]

Hi All,

I am in the process of buying a gear selector stick as have same fault but have run into a problem , does anyone know please how to take the plastic gaurdring around the gear stick, I need to do this to get access to the screws. Does the guarding around the wheel just pull apart or it held together by screws.

regards
riz

[Theo]

Hi AlienC4
Your tip with the brake and flippers worked for me as well. Except it does not go into reverse. But I could force neutral and then start. I decided to fully debug my problem and found the problem to be the gearbox ECU. I must mention that my car is a Peugeot 508 but I think the gearbox is the same. I"ve found that the control lever is connected to the ECU by 4 wires. If one of those wires has an issue by having the wrong level you get P1718. Valid codes always need two wires to change level. The good thing is you can actually measure these levels with Diagbox. The level should be 2.25V or 3.75V. In my case the ECU did not deliver enough current to the selector. My high level was sometimes less than 3V. I could fix that with a simple resistor.

I explain it in more detail here



It's basically a step by step method to debug this problem and I hope it helps others as well.

[tog1760]

Just another experience. I changed my 12 yr old battery (Citroen Grand Picasso) and discovered the negative terminal clamp severly coroded. This is well hidden until you remove the battery. This wouldnt help the electrically based problems either.