Flashing Glow Plug Light in VW TDI Models
It is true that should your glow light plug light flash or stay on, something is amiss. This warning is different than from the Engine light. You can get engine codes from either depending how good your engine analyzer is. Your GP light may flash and yet you cannot pull any codes, but a VW center can for $100. Your car may actually run 100% fine and get great MPG while the annoying light flashes, creating driver anxiety. This could mean the issue is NOT serious and there is only a bad sensor reading or intermittent failure, and the ECU is using an generic replacement spec that is not the best for the car, but does work fine.
Before you rush to the VW repair shop, a flashing GP light can mean simple things, like a brake light bulb being burned out or the brake light pedal switch going bad. Both are easy fixes, but if you examine them and find out the brakes are fine, it still could be a blown brake light fuse #13. Those are the simplest fixes and cost little.
The VW manual does not tell you what things cause the light to flash (BTW, if the light stays on, it is more serious). Here are some conditions that trigger it:
00741 Brake pedal monitoring - implausible signal
01044 Control unit incorrectly coded
P0321 Engine speed sensor - implausible signal
P0322 Engine speed sensor - no signal
16955/P0571 Brake light switch (F) - implausible signal
P1245 Needle lift sender (G80) - short to earth
P1246 Needle lift sender (G80) - Implausible signal
P1247 Needle lift sender (G80) - Open circuit/short to positive
P1354 Modulating piston movement sender (G149) - electrical fault in current circuit
P1561 Metering adjuster (N146) - control difference
P1570 Engine control unit blocked
P1612 Control unit incorrectly coded
P1618 Glow plug relay (J52) - short to positive
P1619 Glow plug relay (J52) - open circuit/short to earth
P1632 Accelerator position sender - voltage supply
A faulty cruise control or using biodiesel fuel has also been reported to cause the condition. Your GP light may flash for a while and then not flash for awhile and go back and forth. It is likely a more minor issue causing it, especially if the car runs totally fine. I had this condition for months, could not pull any codes, engine light was off. Brake lights are fine. So, I gave up. In pre-2000 TDI models, the light comes on when water must be drained from the fuel filter.
The intermittent flashing GP light is generally not serious, but should be investigated. Is it worth peace of mind and having a VW analyzer pull codes if your analyzer cannot? It comes down to how is the car running-totally fine? Think, a minor issue. Do the simple fixes first and if it continues pay the $100. What other choice do you have?