Quote:
Originally Posted by fireman453
(Post 2040834)
... as soon as the temp gets down around 0Celsius or 32 F for my american friends the car starts fine in the morning and as i start to drive down the road the asr light will come on and the car goes in to limp home mode. throw it into neutral and restart and it will be fine for a bit then does the same again. It will do this four or five times till the car warms right up and then it will be fine for the day.
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Likely Culprit: Coolant Temperature Sensor (which affects idle speed control).
Some consistent behaviors I have observed with my car:
1.) When Re-starting the car, RPMs surge higher than normal. If it surges above 1100 or so, the ASR fault
Will be triggered again. If it goes to around 1000, then slowly eases down, ASR
Might be triggered. If on restart RPM cranks up to about 900 then immediately drops down to about 600, ASR fault will
Not be triggered.
2.) When restarting, but before cranking, a relay “ping” can be heard from the vicinity of the rear center seat, where the fuel tank is. It sounds exactly like the relay that trips when the seat heaters are turned on, (except that sound is from the rear left).
3.) The ASR fault does not go away until coolant temp baselines at 80C-82C. The test I would use is to simply turn on the windshield defogger and watch the temp needle. If it drops below 80, coolant is not yet warm enough. If it lands on 80 or above, it is.
4.) After driving a short distance, with coolant still less than 82C, and I stop and do some shopping or other activity that takes longer than 10-15 minutes, when I come out and start the car, it will be just fine (because heat soak has warmed the sensor).
The brake switch itself is not the issue; removing your foot from the accelerator, and the subsequent drop in RPM before your foot touches the brake, is. Sensory input to the computer does not correspond to its set of "Known Acceptable Behaviors," so it triggers the ASR fault. Also, if on the first start of the morning, you rely on the car’s own traction and don’t touch the accelerator when backing out and moving forward, you will Not trip the ASR at all, even if you repeatedly apply the brakes. Only after you engage the accelerator, rev the engine, let up (or upshift) and RPMs drop down, is the ASR fault tripped.
The brake switch is not the culprit, but is nonetheless involved in the process -- “involved” because it can be a trigger for other events, and also applies an electrical load. For example:
At the threshold where the car is almost warmed up, but not fully warmed up, the ASR fault may or may not occur depending on whether or not you apply a substantial electrical load. In my experience, restarting the car when it was warmed up (but not fully warmed up), cleared the ASR light and everything behaved normally, unless I turned on the radio or A/C (or both) and hit the brakes, which tripped the ASR. The power draw is apparently interfering with or diminishing sensor output. After shutting off radio/AC, restarting, driving/idling a few moments, the coolant becomes fully warm, and additional electrical loads don’t have any impact (perhaps because the computer is no longer attempting to regulate idle speed?).
If you speak to the previous owner, he will likely tell you the problem first occurred on a sub-freezing day and progressively got worse. You may also notice the problem is worse if the car sits in the rain overnight.
