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Both the yellow brake light and the DSC light started showing up occasionally for about a week ago and yesterday the light didn't disappear at all so I chose to scan the car using INPA and got the following error code "5E20 pressure Sensor 1 electrical failure". I just ordered a new sensor but, which one is "Sensor 1"? It was a real struggle for me to move the E box out of the way so that I would have room enough to fit a 27mm wrench down there. So I will happily not do all that again just because I changed the wrong sensor. Searching around everyone seems to agree that nr 1 is the one furthest away from the master cylinder or the brake booster, that also makes sense since that would be the same order as the cylinders. But no one has actually confirmed this.

I haven't done this yet since the 17EUR sensor from Lithuania hasn't arrived yet. Therefore would be happy if anyone who had the same problem could share how he solved it. As of right now, I'm planning to remove the brake line above the sensor as it's in the way for me to fit a wrench down there. Then I will quick as hell fit the new sensor and refit the brake line, does this seem reasonable? I'm doing a brake flush right after I solve this problem.

Btw I got my ideas from this guy: E-box removal.
 

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2004 330Ci 85k miles
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Before you dive right into assuming the sensor is bad and changing it, maybe look at its value (brake pressure) in INPA on the ABS page?
Maybe also use a multimeter to check it’s signal in the wiring harness? It may only be available right at the ABS connector.
 

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Discussion Starter #3
Before you dive right into assuming the sensor is bad and changing it, maybe look at its value (brake pressure) in INPA on the ABS page?
Maybe also use a multimeter to check it’s signal in the wiring harness? It may only be available right at the ABS connector.
I tried to find the values in INPA but couldn't find where. I did find "<F5> read pressure sensor" but when I hit F5 nothing happens. Am I looking in the wrong place?
905747
 

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Discussion Starter #4 (Edited)
Before you dive right into assuming the sensor is bad and changing it, maybe look at its value (brake pressure) in INPA on the ABS page?
Maybe also use a multimeter to check it’s signal in the wiring harness? It may only be available right at the ABS connector.
Okay, I found it. With the car turned on the pressure in brake circuit 1 stays around -0.48 bar and circuit 2 at -1.33 and when I press the brake circuit 1 goes to 64.96 bar and circuit 2 goes up to 63.68 bar. This means that the sensor is giving some kind of output. So what now? Should I not bother changing the sensor, are the numbers normal? If so I'll have to troubleshoot elsewhere.
 

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That shows both pressure sensors are working, which is what I suspected.

What year and model E46 do you have?

I ask because some years and models are very prone to have the ABS control module go bad.
When my E39 ABS module went bad, it threw an error code for brake pressure implausible. My ABS codes reported by BMW Scanner 1.4 were these.
73 - Pressure Sensor interference
69 - Brake light switch plausibility
That car has the same ABS system as the 325xi/330xi, the Bosch 5.7.
I replaced the sensor - it was NOT cheap - yet the problem was still there, same error code.
Turned out the ABS module needed to be rebuilt, and that fixed it.

The Bosch 5.7 and early MK60 (especially 2002) seem to be much more likely to fail than later (2004+) models.

One of the ways to detect this type of ABS module failure is when it throws codes of sensor signals missing, yet those signals are properly present at the ABS module connector. These modules have internal connections and bonding wires that break with time, heat, vibration.
 

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Discussion Starter #6
That shows both pressure sensors are working, which is what I suspected.

What year and model E46 do you have?

I ask because some years and models are very prone to have the ABS control module go bad.
When my E39 ABS module went bad, it threw an error code for brake pressure implausible. My ABS codes were these.
73/FF - Pressure Sensor interference
69/FF - Brake light switch plausibility
That car has the same ABS system as the 325xi/330xi, the Bosch 5.7.
I replaced the sensor - it was NOT cheap - yet the problem was still there, same error code.
Turned out the ABS module needed to be rebuilt, and that fixed it.

The Bosch 5.7 and early MK60 (especially 2002) seem to be much more likely to fail.

One of the ways to detect this type of ABS module failure is when it throws codes of sensor signals missing, yet those signals are properly present at the ABS module connector. These modules have internal connections and bonding wires that break with time, heat, vibration.
I have a 04 320i, as far as I know the ABS module isn’t known to break on my year and model.

Since I don’t know how long my brakes have been on the same fluid nor if it have been properly bleed. I’m gonna be doing a complete brake fluid flush and then bleed the brakes using INPA. Might this do some good for the issue I’m having?


I also want to
mention that about two month ago I installed coilovers, I’ve heard that new especially lower suspension can mess with the Dsc system.
 

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Always good to regularly flush/bleed the brake fluid. I don’t see that fixing your trouble code, but ya never know.
Might be useful to further characterize when the code gets thrown, the conditions, how often, etc. Is it intermittent?

I just re-read your first post and noticed the trouble code description.
5E20 pressure Sensor 1 electrical failure
Seems to be pointing to the wiring or related electronics.

If your master cylinder and ABS module are easily accessible, carefully check all the wiring. Wires break, rodents chew, etc.
 

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Discussion Starter #8
Always good to regularly flush/bleed the brake fluid. I don’t see that fixing your trouble code, but ya never know.
Might be useful to further characterize when the code gets thrown, the conditions, how often, etc. Is it intermittent?

I just re-read your first post and noticed the trouble code description.
5E20 pressure Sensor 1 electrical failure
Seems to be pointing to the wiring or related electronics.

If your master cylinder and ABS module are easily accessible, carefully check all the wiring. Wires break, rodents chew, etc.
I put everything back together and drove for almost a week without the lights turning on. But today, after driving for about 40 minutes the lights turned on again. Just like every other time they turned on it’s after I’ve been driving for awhile. They never turn on right away. Seems like they only turn on after braking a few times. When the brakes have gotten warm.

I scanned the car checking the error codes. Now instead of SE20 the error code was “SE24 Druck Sensor 1/2 unplauaibel”. The pressure sensor remains to give output, so they are still fine.
 

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So you're getting a warning that the signal was Implausible. Common for a bad switch or connection. Could also be the unit.

The problem is to try to catch the data at the time it happens.

Switches are cheaper and I might be inclined to change them and see if your intermittent issue goes away?
 

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Discussion Starter #10
So you're getting a warning that the signal was Implausible. Common for a bad switch or connection. Could also be the unit.

The problem is to try to catch the data at the time it happens.

Switches are cheaper and I might be inclined to change them and see if your intermittent issue goes away?
Switch, What is that? And how do you replace them? I haven’t checked the resistance on the sensors but since I can see them showing values in inpa I have a hard time believing it’s the sensors fault. Might be a lose connection between the unit and the sensors.

(The problem only occurs when it’s rather hot outside.)
 

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Sensors and/or two switches. Different name, same parts.
Yes could be the resistance of the connections anywhere along the line. Could also be the resistance of the switches themselves?

About the only "easy" things you can try:
Remove all of the connections & look at them. Clean and apply Stabilant to the pins.
Change the switches.

If the issue returns you will have to become a detective and figure out why.
 

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Discussion Starter #12
The problem is to try to catch the data at the time it happens.
I managed to catch the data shortly after the light turned on. The offset pressure brake circuit 1 was in the red area. It stayed around 5.40 bar. So I have to high pressure in one brake circuit. What does that mean and what could cause it?

906517
 

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Assuming this capture happened when you are NOT stepping on the brakes?
I'd be checking the connections and/or replacing that switch....
 

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I have the same ABS unit on my 2005 Z4.
I had the exact same code in summer 2018. Like you I was able to catch the sensor when it was mis behaving and throwing the code (careful planning and carrying the computer in the car with me).
Actually what stroke me at the time is not the big offset, but the fact that for the two sensors live readings one reading was completely erratic, typically oscillating between 0 and 10 bar. This happened when I was depressing the pedal, I could see the pressure increasing but also oscillating.

I replaced the sensor that gave me erratic data and it has been all good for the last two years.

It is a good occasion to flush the brake system thoroughly. If you don't want to wait until the sensor come you can always flush the brake fluid and check for a sticky caliper that would make one brake circuit heat faster than the other and therefore increase the pressure.
 

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Discussion Starter #15
I have the same ABS unit on my 2005 Z4.
I had the exact same code in summer 2018. Like you I was able to catch the sensor when it was mis behaving and throwing the code (careful planning and carrying the computer in the car with me).
Actually what stroke me at the time is not the big offset, but the fact that for the two sensors live readings one reading was completely erratic, typically oscillating between 0 and 10 bar. This happened when I was depressing the pedal, I could see the pressure increasing but also oscillating.

I replaced the sensor that gave me erratic data and it has been all good for the last two years.

It is a good occasion to flush the brake system thoroughly. If you don't want to wait until the sensor come you can always flush the brake fluid and check for a sticky caliper that would make one brake circuit heat faster than the other and therefore increase the pressure.
Nice to hear someone that had the same problem. The weird thing with my sensor is although it’s offset it’s not erratic. Watching the parameter the pressure stays roughly around the same value, both with no pressure and with pressure on the brake. it stays just as still and precise as the other brake circuit. This is what makes me suspect it to be something else’s fault rather than the sensor. Will definitely check for a sticky caliper, that would also explain why my car slightly drags to the side when I’m braking.

Finally, which nr sensor did you replace? I believe sensor 1 is the closet to the firewall.
 

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I think I replace sensor 2. I basically identified the circuit by unplugging the sensor while watching live data and looking which sensor suddenly stopped reporting. This is the best way to be sure.
It may be very cramped on the e46, there is a bit more space on the Z4 around the master cylinder so I was able to stick a crescent wrench there.
You may want to just flush the brakes and inspect/clean the caliper guide pins first. The OEM sensor I bought was $160 or something.
 
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