VCDS 16.8.0 no longer showing fault codes it did before (codes not cleared)

2000 Jetta tdi

I have a flashing red thermo dash light and a solid brake sensor light. About a week ago I checked for fault codes and found several. The thermo ones I think were some sort of intermittent issue and the brake one had to do with intermittment ABS connection. I did not clear the codes and unfortunately was in a rush and didn't save them. Today I have scanned all controllers and cannot find these fault codes any more. I did not clear them before. Visually, all four brakes look good and the Master Cylinder is full up. I think I do have a leak in my cooling system, but the code(s) should still be there, right?

I've tried this on VCDS 16.8.0 and 16.8.1, same results. What could I be missing here? How can fault codes "disappear" but still showing dash indicator lights?

Thanks for any insight you can offer.

The faults you saw previously may have been intermittent and not recurring. After x number of engine cycles without a repeat fault, the fault is cleared on it's own.

The warning lamps don't necessarily run through the ECU and therefore there's nothing to 'store' or report.
Your hand brake warning lamp doesn't produce an ECU fault code does it? Ditto for the coolant level in the pressure sphere, or brake fluid level in its reservoir.

Those are not VCDS codes. The flashing thermo light is low coolant and the solid brake light if its the one I am thinking, is the low brake pad sensor or e-brake on or low fluid as suggested above.

Lug_Nut said:

The faults you saw previously may have been intermittent and not recurring. After x number of engine cycles without a repeat fault, the fault is cleared on it's own.

The warning lamps don't necessarily run through the ECU and therefore there's nothing to 'store' or report.
Your hand brake warning lamp doesn't produce an ECU fault code does it? Ditto for the coolant level in the pressure sphere, or brake fluid level in its reservoir.

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Thanks for clarifying this. Makes sense. Yes, I do believe the ABS brake code was an intermittent one. It was odd though, the particular ABS fault code I saw was not listed under the ABS control module, but I don't remember which module it was.

turbovan+tdi said:

Those are not VCDS codes. The flashing thermo light is low coolant and the solid brake light if its the one I am thinking, is the low brake pad sensor or e-brake on or low fluid as suggested above.

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Thanks. The flashing thermo light has been going for over a year now. Temp never gets above 190. The coolant is low enough that I am only having intermittent cabin heat through the vents. I just put some fresh coolant mix in the other day and the pressure globe is now almost empty already, but not quite. I will try putting some more in and see if it stays. I probably have a slow leak and am trying to figure out if it's something I think I can fix myself or if it needs a shop.

The solid brake light is amber colored (like the light on the left in this image), with a circle in the middle with a partial concentric circle outside of that. Owners manual just says the brakes need servicing. Master cylinder is full. The car is braking fine, all four pads look in excellent condition. I had the e-brake cable replaced about 5 years ago, rear pads and rotors about 4 years ago. Odd thing was after the rear brake job, I brought it home, set the e-brake and stupidly left it in neutral (standard trans). A few hours later, I came out to find my car in my neighbors flower garden, a small tree stopped it from rolling further. I called the shop who had done the brakes and they were cautious to not accept fault, as they had done nothing with my e-brake. I called the shop (a different one) who had replaced the e-brake cable and they said the cable was non-adjustable. I've never heard of a non-adjustable e-brake before, but I'm no car expert. I took the car into them for another reason (nothing to do with the e-brake) and oddly enough after that visit, the e-brake was tighter. So perhaps there's something screwy with my e-brake? It has never failed again since it was "tightened" but then again I'm not sure I've since parked it without being in gear.

Especially on an older Mk4 like yours there are a few warning lamps that are pretty simple and no scan tool interaction. Brake wear, brake (fluid level, parking brake), oil pressure, coolant level/overheat, etc. are good examples.

Amber brake warning is brake pad wear only. There should be an electrical connector in driver inner brake pad on front axle. Some shops will save a few pennies and use pads without the sensor. Result is you get to stare at the warning light and the first warning of worn brake pads is the loud screeching of metal to metal contact (assuming a regular inspection misses it).

Flashing coolant light is for level and/or overheating. Sounds like pretty obvious you have a bad leak. A slow leak needs a cup every month or three. A bad leak the bottle is empty in a day or two. Bright side is that pink coolant leaves a pretty obvious trail when it leaks (you put in pink, right?). I would normally hazard a guess at the flange on the driver end of the cylinder head, but ALH is not as common failing there as the other cars.

Side note - sometimes coolant temp gauge won't report very high temp and you won't get much heat, BUT the car is actually over heating. If coolant is low enough then not enough flow at temp sensor will result in false readings. And how is coolant removing heat from hot engine if there is not enough there? Certainly not making it into the car so you have heat.

Brake cables are adjusted under the arm rest (if you have it) right behind the parking brake handle. Should be adjusted to start feeling resistance within a couple clicks. BUT big part is to make sure lever on rear calipers is returning to rest position. I forget the exact measurement but I like it almost touching if not fully resting on the stop. If the cable is too tight or the caliper is sticking (or spring broken) then brakes will drag.

Jason

Lug_Nut said:

The faults you saw previously may have been intermittent and not recurring. After x number of engine cycles without a repeat fault, the fault is cleared on it's own........................

Click to expand...

Thought the codes stayed in memory until cleared.
I know the CEL does behave as you describe.