2003 2.5i, yellow brake light, DSC, and tire pressure lamps on hot days

T

tkvoice

Member
 Minnesota
My 2003 E85 turns on 3 warning lights yellow brake light, DSC, and tire pressure. After sitting parked in the sun on hot days (85F/30C).

I do keep a ODB reader in the car and no DTC are set when this occurs.

After sitting over night (and cooling down) all the lights are off when it starts. I can drive around all morning without any warning lights.

I have checked my air pressure on the tires and all is good.

Any ideas?

17751.jpg
 
Just have a basic ODB scanner in car, it can't get to the module level.

I do have INPA but then I would have to drag my laptop around waiting for it to happen. I tried with INPA when I get home but by the time I get it all set up the lights are off and no codes are set
 
Would making sure the tyre pressure memory thing has been reset, the button next to the roof buttons. If the pressure is set low and the tyres heat in the sun and the pressure increases would this upset the car. Long shot?
 
MikeyH said:
Would making sure the tyre pressure memory thing has been reset, the button next to the roof buttons. If the pressure is set low and the tyres heat in the sun and the pressure increases would this upset the car. Long shot?
Click to expand...
If the tyre light is yellow it means there's a fault in the system. If a tyre loses pressure the light is red.
 
Exactly the same thing happened to me last week with the hot weather. I read that this can be caused by the DSC brake pressure sensors connections attached to the reservoir. I pulled them off and cleaned them and the issue like the hot weather has vanished . If this returns I may replace the sensors next and change the break fluid
 
Happened to me too. I got a code for a wheel speed sensor and planned to replace it but the lights went away soon after so I didn't bother. Wonder if high temperatures temporarily disrupt the sensor?
 
PeterA said:
Happened to me too. I got a code for a wheel speed sensor and planned to replace it but the lights went away soon after so I didn't bother. Wonder if high temperatures temporarily disrupt the sensor?
Click to expand...
Oh s**t. I hope not or I will have to retrieve my wheel sensor from the bin and will not be happy splashing £120 on a new one. :headbang:
One of mine started playing up when the weather was hot!
 
Did the tire pressure reset and it did not help.
MikeyH said:
Would making sure the tyre pressure memory thing has been reset, the button next to the roof buttons. If the pressure is set low and the tyres heat in the sun and the pressure increases would this upset the car. Long shot?
Click to expand...
 
Finally had time to pull out my laptop. Got INPA up and running. Its the DSC module:



E R R O R M E M O R Y
---------------------------------------
Date: 07.06.2026 11:23:17
ECU: DSC_MK60
JobStatus: OKAY
Variant: DSC_MK60
-------------------------------------------------------------
RESULT: 1 error in error memory !
-------------------------------------------------------------
5E30 Querbeschleunigung Sensor elektrisch defekt
Error counter: 1
Logistic counter: 40
Mileage 177570 km
Fahrzeuggeschwindigkeit 0.00 km/h
Bremslichtschalter 0.00 0/1
Bremsfluessigkeitsschalter 0.00 0/1
ASC/DSC_aktiv (Tasterfunktion) 1.00 0/1
Bremsdruck erkannt 0.00 0/1
ABS-Regelung 0.00 0/1
ASC-Regelung (BMR) 0.00 0/1
ASC-Regelung (AMR) 0.00 0/1
GMR-Regelung (GMR) 0.00 0/1
GMR-Regelung (MMR) 0.00 0/1
CBC-Regelung 0.00 0/1
MSR-Regelung 0.00 0/1
TDR-Regelung 0.00 0/1
SDR-Regelung 0.00 0/1
DBC-Regelung 0.00 0/1
RTA aktiv 1.00 0/1
Run-Up Mode 0.00 0/1
kein passendes Fehlersymptom
Testbedingungen erfuellt
Fehler momentan vorhanden und bereits gespeichert
Fehler wuerde das Aufleuchten einer Warnlampe verursachen
Error code: 5E 30 E0 01 28 45 5D 00 08 00 04
=============================================================

Here is what Copilot came up with:

🇩🇪 → 🇺🇸​

kein passendes Fehlersymptom​

No matching fault symptom → INPA didn’t find a predefined symptom category for this error.

Testbedingungen erfüllt​

Test conditions fulfilled → All required conditions for this diagnostic test were met (speed, ignition state, sensor plausibility, etc.).

Fehler momentan vorhanden und bereits gespeichert​

Fault currently present and already stored → The fault is active right now and also stored in memory.

Fehler würde das Aufleuchten einer Warnlampe verursachen​

Fault would cause a warning lamp to illuminate → This is a lamp‑relevant fault (DSC/ABS light should be on).


🔍 About the hex string​

Error code: 5E 30 E0 01 28 45 5D 00 08 00 04

This is the full BMW DSC fault frame, not the actual fault code.The real fault code is the first two bytes:

5E30 — Pressure Sensor 1 / Brake Pressure Sensor Plausibility​

This is a very common E85/E46 DSC failure.


🧠 What 5E30 means on your Z4 (E85)​

BMW DSC uses a dual‑channel brake pressure sensor inside the DSC hydraulic unit.5E30 indicates:

  • The pressure sensor signal is implausible,
  • Or the two internal channels don’t agree,
  • Or the sensor is out of range.
On the E85, this is almost always:

✔ Internal DSC pressure sensor failure (hydraulic unit issue)​

NOT the external brake light switch, not wheel speed sensors.


🧪 Typical symptoms​

  • DSC light on
  • ABS light on
  • Brake warning light may also appear
  • DSC/ABS disabled
  • Sometimes intermittent at first, then permanent
 
I don't understand? What is a pre facelift car?

Are the pressure sensors mounted inside the DSC/ABS module or are they external? Seeing as the failure is only when car gets hot it might just be a bad soldering joint.

Has anyone replaced DSC pressure sensors or tried re-soldering or cleaning connectors (pictures would help if available)
 
JIF said:
Exactly the same thing happened to me last week with the hot weather. I read that this can be caused by the DSC brake pressure sensors connections attached to the reservoir. I pulled them off and cleaned them and the issue like the hot weather has vanished . If this returns I may replace the sensors next and change the break fluid
Click to expand...
Hi Jif

Is there any way you can post a picture of the DSC connectors you pulled and cleaned?
 
tkvoice said:
I don't understand? What is a pre facelift car?

Are the pressure sensors mounted inside the DSC/ABS module or are they external? Seeing as the failure is only when car gets hot it might just be a bad soldering joint.

Has anyone replaced DSC pressure sensors or tried re-soldering or cleaning connectors (pictures would help if available)
Click to expand...
Your car will be a pre facelift because of age

The sensors are mounted here in this image you will see them near your brake fluid reservoir

There are two
IMG_3863.png
 
The inpa error says:

5E30 Querbeschleunigung Sensor elektrisch defekt

Which translates to:

5E30 Lateral acceleration sensor electrically defective


... So CoPilot is probably hallucinating. (how can error 5E30 be pressure sensor #1) When the direct translation says "lateral acceleration sensor"?

Where do I go to find authoritive source for error code 5E30?
 
Ah- that’s on me my mistake

Your lateral acceleration sensor is the unit that sits under the right hand seat…

That usually means it’s succumbed to water ingress at the door where the vapour barrier has failed and is now probably sat under soggy carpet

Check that
 
enuff_zed said:
Facelift ones are. Getting around £200 secondhand.
However the OP has a pre-facelift car and the 'yaw sensor' for those can be had for £50 or less, secondhand.
Click to expand...
I was quoted over £900 for both sensors for my Z3 from BM|W (new obviously).
Managed to find both second hand but still paid over £300 for the pair.

I would imagine the Z4 ones are very similar as my car has DSC.

And, yes, mine were both knackered from swimming in water!
 
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