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Discussion Starter · #1 ·
I found out some interesting things.

First off, this is a composite dyno graph generated by the ECU. I didn't know it could do that. Assuming it's at all accurate, it looks like my engine is just about in perfect stock tune -- or else I have no idea what I'm talking about.



When I say it's a composite, I mean that I drove the car for a while, pulling down some 1400 data points, and I grabbed all the data points recorded during a throttle position of 80 degrees or higher to create this graph.

The engine has almost 94000 miles on it, for the record, and about $3000 in renovation since I purchased the car.

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I also found a few error codes in various modules:

Address 02: Auto Trans
Part No: 8D0 927 156 BM
Component: AG5 01V 1.8l5VT USA 8508
Coding: 00000
Shop #: WSC 00000

1 Fault Found:
00526 - Brake Light Switch-F
27-00 - Implausible Signal

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Address 03: ABS Brakes
Part No: 8E0 614 111 B
Component: ABS/EDS 5.3 FRONT D10

1 Fault Found:
01203 - Electrical Connection between ABS and Instrument Cluster
31-00 - Open or Short to Ground

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Address 17: Instruments
Part No: 3B1 919 930 GX
Component: B5-KOMBIINSTR. VDO V01
Coding: 06242
Shop #: WSC 09427

1 Fault Found:
00779 - Outside Air Temp Sensor (G17)
30-00 - Open or Short to Plus

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Address 46: Central Conv.
Part No: 1J0 959 799 AJ
Component: 63 Zentral-SG Komf. 0001
Coding: 04096
Shop #: WSC 05311

3 Faults Found:
00943 - Heated Exterior Mirror; Driver Side (Z4)
35-10 - - - Intermittent
00912 - Window Regulator Switch; Front Left (E40)
27-10 - Implausible Signal - Intermittent
00944 - Heated Exterior Mirror; Passenger Side (Z5)
35-10 - - - Intermittent

My cruise control doesn't work; would it be reasonable to assume the brake light switch fault is the reason why?

The ABS error code confuses me, though. I can't tell if it's related to the brake light switch, or if it's something else. I DO know that both the BRAKE and ABS lights on the dashboard work (because they blinked when I checked the DTCs), and I know the ABS works because it's activated itself recently. No flashing lights when the ABS engages, though; does that matter?

The outside air temp sensor fault is also bothersome. It actually doesn't tell the whole story, because not only doe the air temp sensor not work, but the miles-per-gallon readouts don't work either. Oh, and the combo switch that controls the readouts works sometimes and not others. Am I looking at a new CCM, or a new gauge cluster, or is it more likely that I just have some loose wires?

I doubt the mirror codes are valid anymore; I replaced them recently, and discovered to my delight that the heated mirror switch actually does work. The window switch code is certainly valid, though, because it's been getting worse and worse. I think I need to clean it.

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And lastly, I have a nice chunk of raw data that I have almost no idea how to interpret, save for the torque/rpm numbers. Here's the data fields I collected:

Timestamp
RPMs
Coolant Temp °C
Oxygen Sensor Control %
Adjustment Conditions
Torque N*m
Timing Retard Active/Inactive
Airflow grams/sec
Timing Angle °
Ignition Timing °BTDC

Is this data sufficient for someone to help me tell whether my fuel, air, and emissions systems are working properly? If not, what do I need to log?
 

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I just fitted cruise control and it didn't work until I replaced the switch but did if I hooked my foot under the pedal and pulled it up a few more mm.
I fitted the new one and it was the same, I think it's due to the aging brake system having too much play. I managed to get the switch adjusted until it works. It screws in and out, but if I were to pull the pedal up, It would slip on a ratched out of adjustment again.
 

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I'm Urlik's Hero
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Regarding the fault codes, save them, clear them and do some more driving.

Do another scan after a few '00 miles and check which codes are still valid. Go from there.
 

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Discussion Starter · #4 ·
I just fitted cruise control and it didn't work until I replaced the switch but did if I hooked my foot under the pedal and pulled it up a few more mm.
I fitted the new one and it was the same, I think it's due to the aging brake system having too much play. I managed to get the switch adjusted until it works. It screws in and out, but if I were to pull the pedal up, It would slip on a ratched out of adjustment again.
Great. Of all the parts on the car that are designed to fit just-so, the brake light switch has to be adjusted.
 

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Discussion Starter · #5 ·
Regarding the fault codes, save them, clear them and do some more driving.

Do another scan after a few '00 miles and check which codes are still valid. Go from there.
Yeah, that was pretty much my plan, though I think I'll replace the brake light switch anyway; it's been to blame for the cruise control failing on every car I've ever seen it fail on.

Any idea whether the data I logged is the data I need to check my A/F ratio?
 

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...Any idea whether the data I logged is the data I need to check my A/F ratio?
You have an AEB, right? If so, the way to check for A/F is to log block 002 (or any block that logs RPM, but 002 gives useful info) and block 031 (O2 voltage) while doing a WOT run in 3rd gear from 2000 RPM to redline (about 25 mph to 80). (You may have to disconnect the kickdown switch to make this work).

Your block 031 readings should be around .865. Not less than .83, not more than .875.
 

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Here's what I do to calculate A/F ratios from vag-com data, I don't know if it's accurate but here it goes. I'm logging block 003/102 at the same time in a 3rd gear wot run. You'll have to know the injector flow at 3 bar (cc/min), fuel pressure (bar) and specific fuel weight/cc (I always use 0.73 g/cc).

Inj. DC = 100*Inj. on time / (120000 / RPM). If the Inj. DC is larger than 100% I'll truncate it to 100%.

A/F ratio = MAF (g/s) / Injected fuel (g/s)

Injected fuel = 4 * Injector flow/60 * SQRT (Fuel pressure/3) * Fuel specific weight/cc * Inj. DC/100

This calc doesn't take the fuel trims into account.
 

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Discussion Starter · #8 ·
Here's what I do to calculate A/F ratios from vag-com data, I don't know if it's accurate but here it goes. I'm logging block 003/102 at the same time in a 3rd gear wot run. You'll have to know the injector flow at 3 bar (cc/min), fuel pressure (bar) and specific fuel weight/cc (I always use 0.73 g/cc).

Inj. DC = 100*Inj. on time / (120000 / RPM). If the Inj. DC is larger than 100% I'll truncate it to 100%.

A/F ratio = MAF (g/s) / Injected fuel (g/s)

Injected fuel = 4 * Injector flow/60 * SQRT (Fuel pressure/3) * Fuel specific weight/cc * Inj. DC/100

This calc doesn't take the fuel trims into account.
What are the fuel trims, exactly?
 

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Discussion Starter · #9 ·
You have an AEB, right? If so, the way to check for A/F is to log block 002 (or any block that logs RPM, but 002 gives useful info) and block 031 (O2 voltage) while doing a WOT run in 3rd gear from 2000 RPM to redline (about 25 mph to 80). (You may have to disconnect the kickdown switch to make this work).

Your block 031 readings should be around .865. Not less than .83, not more than .875.
Yes, I have an AEB. When you say I need to log Block 002, is that the same as Group 002 in the VAG-COM software, or is Block 002 actually a single readout within a Group? That is to say, if I want to log Block 031, do I need to divide 031 by 4 (the number of readouts in a Group) to find out which Group to look at?

Anyway, the kickdown switch doesn't need to be disconnected because WOT is achieved before the switch can be activated. The kickdown switch can only activate once the throttle cable is pulled taut -- there is no other way to activate it.
 

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Discussion Starter · #11 ·
Okay, so (in Ross-Tech's terminology) I want to log Groups 002 and 031. Is there an optional third group that would be helpful? I wish I could remember which block I got the torque info from, but I'm drawing a blank and my logged data isn't here at the office.
 

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Logging 3 blocks in one run gives you less measurements/sec (sample rate), 2 blocks is the maximum. I log the blocks 003/102 (for A/F calcs and other values) and 020/115 (knock and boost). 115 isn't an option for you since you have an AEB (no MAP sensor).

Torque info is in block 120 but I don't use that one anymore, it's not acurate.
 

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This calc doesn't take the fuel trims into account.
Thinking about this, the only way to apply the +/- fuel trim from the ECU to the injected fuel is by adapting the injector DC accordingly. The measured injector on time (actual) must be including this trim. Or am I wrong and is the trim applied after the measured injector DC?

The FPR only maintains the same fuel pressure at all situations (vacuum/boost).
 

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Discussion Starter · #14 ·
Logging 3 blocks in one run gives you less measurements/sec (sample rate), 2 blocks is the maximum. I log the blocks 003/102 (for A/F calcs and other values) and 020/115 (knock and boost). 115 isn't an option for you since you have an AEB (no MAP sensor).

Torque info is in block 120 but I don't use that one anymore, it's not acurate.
The torque isn't accurate with respect to the wheels, or it's not accurate with respect to the engine? If it's measuring torque at the transmission mounts or something like that, that's fine with me -- I can just multiply by .75 to get a reasonable estimate of wheel torque.
 

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The torque isn't accurate with respect to the wheels, or it's not accurate with respect to the engine? If it's measuring torque at the transmission mounts or something like that, that's fine with me -- I can just multiply by .75 to get a reasonable estimate of wheel torque.

I have calculated engine power from that measurement (engine torque) and it was way off / too high.
 

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Discussion Starter · #16 ·
I have calculated engine power from that measurement (engine torque) and it was way off / too high.
The torque is in Newton-Meters. If you're trying to calculate Horsepower, you need to convert the Newton-Meters to Pound-Feet first. Google has the ratios you need.

At first, I was getting a power reading of something like 180HP, bone stock. Then I remembered the whole metric/imperial thing.
 
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