BRM high idle and fan's running

Hey all. I'm looking at an issue I havn't heard much about on an '06 BRM. I noticed the idle running right at 1,000 rpm when stopped. I thought it was a bit high. Turning AC on or off and varying electrical load doesn't effect it. Coolant temp sensors are reading normal. The only code I'm looking at the could maybe cause this is:

01598 - Drive Battery Voltage
000 - -
Freeze Frame:
Fault Status: 01100000
Fault Priority: 2
Fault Frequency: 157
Reset counter: 17
Mileage: 178022 km
Time Indication: 0
Freeze Frame:
ON
Voltage: 13.35 V
ON
ON
OFF
OFF
ON


The fault frequency is high so that seems to be the reason it idles high a lot. I also started the car this morning, when cold. The idle was normal at first then about 10 seconds after start kicked up to 1,000 rpm and the fans came on. The fans seem to be hooked to the high idle (maybe to ensure cooling when stopped with a higher idle?) regardless of AC status. The alternator showed to be charging around 13.5 volts or so at idle when it was idling high when cold.

It seems obvious to me the alternator is marginal (111k miles) and possibly causing the high idle, but I havn't seen a vehicle handle a low charging voltage in this way.

Also, one thing to note. I think there's a couple related issues on this car causing the high idle. The owner asked me to look at an intermittent rattle noise from under the hood. I replaced the flywheel with a LuK one after the original stripped it's splines out one day. Before the splines stripped it did rattle a little bit so I know what a bad DMF sounds like. This noise sounded a little more like possibly the splash guard slapping a somewhere a little under certain vibrations. Now that the car is out of my driveway at the moment, I started thinking maybe it's the alt pulley that's making the noise. If it's slipping it could possibly be causing the low voltage codes and high idle.

Think I'm on the right track or do they not make that much noise? This noise is only noticeable while doing things like backing up or pulling into a parking spot with a little load on the engine.

I've never run into that before. Where was that DTC? Anything in any of the other modules?

oilhammer said:

I've never run into that before. Where was that DTC? Anything in any of the other modules?

Click to expand...

That was under Cent Electronics. No other DTC pertaining to anything near the engine.

Alt pulley does make a noticable noise. And i was gona say higher idle could be the car senses a charging issue. Not sure if vw does that though.

Maybe two issues: alternator pulley (easy to test) and harness chaffe?

The car is off on a trip right now. When it get's back this week I'm going to check it out. At this point, I'm so confident the problem is the alternator pulley that I may have the owner order the part before returning.

I'll surely follow up with the end result.

Conclusion

banshee365 said:

The car is off on a trip right now. When it get's back this week I'm going to check it out. At this point, I'm so confident the problem is the alternator pulley that I may have the owner order the part before returning.
I'll surely follow up with the end result.

Click to expand...

I have been experiencing the same issues with my 2005.5 Jetta TDI with 117,000 miles currently on the odometer. Yes, my fan will cycle on and off regardless of a/c use while idling. Rpm normally at 800-850, but randomly jump to 950-1100 lately, despite being at normal operating temperature. What was the conclusion/resolution to this issue???

Any conclusion?

No conclusion, because no responses. Another thread that leaves one hanging. My inclination is not alternator issues with my vw, but rather a vacuum line leak. I need to schedule an appointment to have a "smoke test" done to see if there are any leaks. No pending codes present.

ive been having these same issues lately with my 05.5 jetta with 213k miles. it sometimes runs the fans about 20-30 secondas after startup and usually either starts idling high or low just wondering if anyones found the answer yet. ill deffinately check the alt pully.

Had vehicle examined today. Alternator pulley is fine. Vacuum lines are fine. However, a/c fan not coming on with the a/c compressor. In other words, small fan not turning on when the a/c is activated. Big fan works, but is on more than it should to compensate for lack of small fan not working. No CEL on dash, but scanned codes revealed engine code 08581- Engine coolant temperature sensor 2 signal too high, value of resistance too great. Technician needs further time to diagnose and trace vehicle's wiring and to check for bad ground or wire chafing.

Would a bad a/c fan cause the vehicle to send engine code 08581? Could the solution be as simple as a repair of the small a/c fan or replacement if it has failed?

Replaced coolant temperature sensor in cooling flange as scan tool indicated as bad. Replaced additional coolant temperature sensor in radiator hose as a precaution. Also reconnected this sensor connection to the factory wiring harness, as VW dealership had previously hot wired this senor's two wires (yellow and brown) through firewall directly into ECM in cab for who knows what reason. Tested slave auxillary fan and it was dead, so replaced that as well. Cleared pending code. Tested. All good now. Auxiliary fan comes on when a/c activated. Radiator fan works on low and high speed and RPMs back to normal.

The issue with the car I was working on was the alternator pulley. I replaced the pulley and the rattle went away and the idle returned to normal.

I have the SAME high idle issue. First time I saw this was with a high electrical load in the winter time (normal). Years later, the RPM's randomly rise to 1050 and fans run even before the engine is up to normal temps and with little to no electrical load. I have no codes at all, and voltage measures over 14v. I replaced the coolant temp sensor on the radiator hose just to give it a shot and no change. Where is the other sensor located? and is it the same part# as the other? Really wish I could get this one figured out. Appreciate any input.

chase345 said:

I have the SAME high idle issue. First time I saw this was with a high electrical load in the winter time (normal). Years later, the RPM's randomly rise to 1050 and fans run even before the engine is up to normal temps and with little to no electrical load. I have no codes at all, and voltage measures over 14v. I replaced the coolant temp sensor on the radiator hose just to give it a shot and no change. Where is the other sensor located? and is it the same part# as the other? Really wish I could get this one figured out. Appreciate any input.

Click to expand...

the other sensor is to the right of the engine (driver side), it's the same sensor as the radiator one. It is probably ground that's at fault. I replaced both sensors and nothing, so I relocated my battery back to the engine bay. That fixed it.

The coolant sensor on the engine fixed the issue for me. Thanks!