P0703 Brake Switch B Input Circuit.

**industrialfish** · 03-16-2014

2005 GTP, getting ONLY this code (other than my constant P0420 catalytic code) and my cruise control is intermittent.

This code seems to be a different cause and solution for every make and model so teh interweb hasn't been very helpful for this specific vehicle.

The brake pedal switch is cheap and easy to replace if that is indeed the problem, but it could be the sensor on the master cylinder = $ or the TCC = $$$ or any harnesses in between, so anything else I will just dealership it since I've got like 800 miles left in the warranty, but I wanted to hear from you guys first if anyone has any specific info or firsthand knowledge.

-Matt

**industrialfish** · 03-19-2014

Damn, nobody has any input?

**rgwog** · 03-24-2014

A '05 GTP here too. I thing I may be having the same issue also. I have not checked for a code. Did you you get any kind of check engine light or any thing like that? Mine is surging 100 to 200 rpm cruising at speed, doesnt do it all the time and does seem to stop when you tap the brakes. I have reset the PCM just to see if that was the issue, and no joy there. I do have to agree it is tough to get info for this vehicle. Have you done any thing to correct yours yet?

**industrialfish** · 03-24-2014

My check engine light comes on frequently due to the catalytic issue I have, so I have no idea if the P0703 is setting the light or just storing the code in the computer. Although when I clear my cat code, the brake code isn't always there so I know it's not throwing it all the time.

When it gets warmer, maybe this weekend, I'll be able to fix the problem causing the cat code so I'll be able to narrow down if the brake code is matching any symptoms I feel when driving.

**rgwog** · 03-24-2014

OK, yea I have no ck eng light. So wouldnt have any idea if I was getting a code unless I had it checked. My issue seems to be not so noticeable in the morning first thing but when i get in later on it really acts up. Ill keep an eye on here, let me know what happens on your end. I may just go ahead and get a new brake switch and see what happens. A low cost job and may do it. LOL I just noticed that yours is the same color and wheel style.

**Scottydoggs** · 03-24-2014

you guys got working brake lights? or they work, dont work deal? if so id change the brake switch on the brake pedal. or make sure its in place right and the wires are ok.

ford explorers have a messed up brake switch that would fall apart, then it would also not let the car out of park, or have brake lights. that god they made a replacement switch for that pos.

**rgwog** · 03-24-2014

Yes the brake lights work, but from my understanding of the switch, it has separate contacts for lights and CCT.

**rgwog** · 03-29-2014

Ok, replaced the brake switch and so far seems to have fixed the problem. Drives like a different car. And every thing works as it should. No surging. Will keep you posted!

**industrialfish** · 04-06-2016

Originally Posted by rgwog

Ok, replaced the brake switch and so far seems to have fixed the problem. Drives like a different car. And every thing works as it should. No surging. Will keep you posted!

Long time update. I never saw this reply until I googled the code again and this thread was top of the results. I had no idea our brake light switch is ALSO a brake pedal position sensor. Ordered a new one so lets see if that fixes this code (which I still have).

**rickisrad** · 11-05-2017

I know this is an old thread but did the brake switch fix your problem Industrial Fish?

**industrialfish** · 11-05-2017

I haven't put it in yet... It stopped throwing the code when I put a new PCM in but I'm still getting the same symptoms. I think I'll put the switch in this week when it's not raining.

**mark97564** · 08-01-2021

Bump... I'm having the issue too but only when the car is fully warmed up. I get charging system malfunction on the DIC too if the car is fully warmed up and I turn it off and start it back up within a few minutes.. I'm thinking when the voltage of my car drops below 11.4 volts it's dropping the voltage of the brake circuit too causing the P0703 to pop pop.. when I scan for trouble codes the P0621 pops up first and the P0703 after.. I'm almost positive it's the current sensor acting up since I have a charging issue and brake signal issue when both use the 10 volt reference wire of the BCM . Odd thing is if I bring the rpm up to 1500 for a second and let off the gas the alternator starts charging properly and voltage goes up...

When it's not charging properly the scanner data shows 15% in the f terminal of the alternator, a a quick tap of the gas it will go up to 50%. Also it seems to only happen when the car charging system seems to be in the maintenance mode where no matter what the electrical load is it maintains 12.8 volts

**fmxfreaker9893** · 12-21-2022

i know this is an older post but i have an 06 grand prix gtp and i get code po703 i have replaced the multi function switch i have replaced brake switch and it still has same issue i am at a loss i have no clue what to do next when i put the scan tool to it it says the switch is off for the cruise control i have no other issues besides no cruise control. Also All brake lights operate as intended.

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