Electrical cable voltage drops

Hey all! I'm still fighting this code:

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

It jumps the RPM to 1,050 or so and runs the fans. The transmission acts much different when the idle is bumped up as well. It slips the clutches a lot more. I hate it.

I'm trying to track it down. Without testing voltage drops I replaced the alternator with a Bosch reman as it was original with 300k. The issue remains.

I'm getting .18-.20V drop between the alternator stud and battery positive cable. I'm getting .08V of it on the alternator to fuse box cable and .1V of it on the battery positive cable.

Are these drops within spec or is at least one of them to blame for my voltage dropping below limits triggering this annoying code?

Those vd’s are within spec. Personally anything > 0.5V raises a red flag

How old is your battery?


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mr.loops said:

Those vd’s are within spec. Personally anything > 0.5V raises a red flag

How old is your battery?


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Click to expand...

It's only a couple years old. Genuine VW battery. The car cranks over great cold.

banshee365 said:

It's only a couple years old. Genuine VW battery. The car cranks over great cold.

Click to expand...

Your freeze frame data shows 13.35 V - that’s with the engine running ... correct? You should be 13.5 - 14.7 V with it running

I would take it to a battery shop and have a tested.


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The battery is used for starting and that's pretty much it... once the engine is running the alternator is king.

So, that 13.3 represents what the ECU is seeing from the alternator... the battery is just along for the ride and/or some charging...so if there's voltage issues with the car running they are likely on the alternator/charging side of the system.

Vince Waldon said:

The battery is used for starting and that's pretty much it... once the engine is running the alternator is king.

So, that 13.3 represents what the ECU is seeing from the alternator... the battery is just along for the ride and/or some charging...so if there's voltage issues with the car running they are likely on the alternator/charging side of the system.

Click to expand...

Good catch Vince! Sorry I miss wrote in my above post.
I meant to say alternator not battery.


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All good mon!

Yea, the battery seems fine. I'm getting 13.80V across the charge post and alternator body and 13.30-13.40 across the battery posts.

You need to check the ground side too, with your voltage drop test. I had same problem as you. Main ground cable at the transmission was my issue. From your post, you mentioned testing the positive side but nothing about the negative side.

Maintainer said:

You need to check the ground side too, with your voltage drop test. I had same problem as you. Main ground cable at the transmission was my issue. From your post, you mentioned testing the positive side but nothing about the negative side.

Click to expand...

I checked the main ground and the 3 smaller ones under the air cleaner. They were all super clean for a 300k car.

I may have found the issue. I was getting .40V drop between the alternator post and positive battery post. That is too much to me. I found a large drop on the red positive battery cable between the battery post and fuse box. I wiggled around the cable in different areas and all of a sudden the voltage drop went away and I was getting 13.90V across the battery posts.

I suppose if I get the issue again I will be looking at that cable again.

I hooked leads from meter to alternator hot out, to battery positive post. Set meter in front of windshield started car and started turning electrical loads on, one by one. Meter readings came up a little then stayed stable, well below .5 V. Then switched leads to the case on the alternator to battery negative post, then repeated the same, you could see the voltage add up, each time I turned something on, reading above .5 but not over 1. Had I disabled car from starting, then just cranked the engine over, I'd bet it would have been over the 1 volt easy. I had looked at that ground cable, looked great, of course I had already reinstalled the air cleaner, so I just added another cable from engine block to body ground. That fixed my issue. It made a believer out of me, for not trusting a cable, wire or the terminals by what they look like. Next time I take out the air cleaner, I will cut the insulation off to look at it inside, be cause I'm very interested on what I'll find.

As mentioned previously, I suggest you focus on the voltage being produced by the alternator, it should be around 14.5-14.7V
The voltage drops will be due to the resistance in the cables / terminations which may warrant investigation but i'd definitely start with the alternator.

TdiTaff said:

As mentioned previously, I suggest you focus on the voltage being produced by the alternator, it should be around 14.5-14.7V
The voltage drops will be due to the resistance in the cables / terminations which may warrant investigation but i'd definitely start with the alternator.

Click to expand...

The alternator is a new Bosch reman. It puts out 14V or so 100% consistently. The issue is what voltage the battery was seeing.