12 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHPSM/ABS "Failure"...when I turn the headlamp switch on
Leading reported evidence
Replace brake fluid
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
PSM/ABS "Failure"...when I turn the headlamp switch on
Read full discussion summary
Leading evidence: 'Replace brake fluid' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'maf as well' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Check brake light switch' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
PSM/ABS "Failure"...when I turn the headlamp switch on
maf as well
Suggestion or failed attempt
No successful repair reported for this finding.
0
Identified cause
1
Suspected cause
0
Reported fixes
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that suspect a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suspected cause
I thought it was the MAF as well and then I changed out the tires (new ones) and the warning never came back.
PSM/ABS "Failure"...when I turn the headlamp switch on
Check brake light switch
Suggestion or failed attempt
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
PSM/ABS "Failure"...when I turn the headlamp switch on
Check metal contacts inside the bulb fittings
Suggestion or failed attempt
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
Also check the metal contacts inside the bulb fittings.
PSM/ABS "Failure"...when I turn the headlamp switch on
Coverage and how to read this overview
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
12 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T174436Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
...the weirdest thing just started happening today on my 02 C4S with ~40K.
As I am driving, I decide to turn on my headlights as it was getting a bit dark. I tap the brakes and immediately the PSM/ABS failure light turns on. Interesting coincidence, until I pull over and attempt to turn the car off... and it refuses to turn off...even with the key fully removed. The car finally turns off only after I turn off the headlight switch.
Everythings "seems" fine otherwise, except for this weird electrical gremlin.
My game plan (already planned for this week separate from this new situation):
Replace 4x brake discs
Replace 4x brake pad sets
Flush brake fluid
install new OEM air box
I will most likely clean MAF as well too
I might replace the presumably 18 y/o fuses as well
Any other thoughts?
why replace fuses if they aren't blown? Check your tires. I had one tire in the past losing traction on this one ramp and that was throwing the PSM/ABS warning/light, etc. I thought it was the MAF as well and then I changed out the tires (new ones) and the warning never came back.
I think one tire was aging more than the others.
Good to know in the tire front. Will double check pressures and such.
The weird thing is how the car won�t turn off via the key/ignition switch when this failure light is on...
Same question as in the other ABS/PSM topic:
Any fault codes popping up with the issue you have?
Also might check your brake light switch. But depends on the codes you have.
All lights working properly? Could be a faulty wire harness. Also check the metal contacts inside the bulb fittings. They tend to break and initially cause bad contacts and then fail.
MAF could be in play. Cleaning might not help. If it is a long time that it was not replaced I would suggest you do it anyway along the way. If you could read the MAF hot film Voltage with ignition on it gives an indication. Should be ideally 1.00V plusminus 0.05V (factory has 0.1V margin).
Have you replaced any of your taillight bulbs lately? I've had a problem once that the engine could not be turned off with a pressed in brake pedal wich turned out to be that one of the double fillament brakelight bulbs was replaced with a single fillament bulb shorting out both contacts in the bulb holder. Just check it before you start digging deeper.
This is great. Thanks folks. I�ll start to go down the list here. Was reading in the other ABS/PSM threads about the brake switch and general brake light issues. I�ll have a look and get update asap
Updates:
Flushed/changed brake fluid
Changed front pads/sensors
Installed new brake light sensor
No change in issue
What I have further discovered is the issue also pops up when the car is idling, no brakes applied, and i simply switch to “parking lights”. There is a bulb out on the front right headlamp. When I switch to full “lights on”, the brake lights immediately turn on and stay on. Even without applying the brakes.
My thoughts for next is to replace the front bulb and have a look see at the condition of the rear bulbs.
This is fun :-)
Very interesting... It has been documented that the ABS/PSM warning can be triggered by low voltage situations and/or damage to the wiring harness. How old is your battery? Could you have it tested easily? I wonder if turning your headlights on is creating enough of a draw off of the electric system to trigger a low voltage situation.
If your battery is strong, do you live in an area where mice or rodents could be an issue?
Good question. I'll check this afternoon, but the voltage meter on the dash looks "good" at 14v. Ill check though with a proper meter.
My gut is weird bulb harness stuff going on + dead bulbs.
This is a source reference. Confirm exact model applicability in the original material.
