Car is a Mk2 Octavia 1.9TDI 105ps DSG

 

Since I've had it (about a year), I've had the following fault and an engine light on the dash.

 

 

000258 - Mass Air Flow Sensor (G70) 
               P0102 - 000 - Signal too Low

 

Live data reads 0 at any engine speed. 
 

I originally assumed it was a faulty sensor, so I changed it for a Chinese one, which I think knocked the light off for a few hours (long enough for an MOT test), then it came back on, so I assumed the sensor wasn't great. Today, I live-data'd the MAF on a scrap Ibiza I've got in the yard, and it seemed to be working (went up and down as the engine speed did). The part number was the same except the suffix (-B on the Octavia, none on the Ibiza), so I decided to give it a try and throw it on. I cleared the codes on the Octavia, and the light came back on shortly after, with the same code, and reading of 0, regardless of engine speed.

 

Here's the engine codes it's giving. The overboost is a new one, but I do remember nailing it with the trailer on a couple of weeks ago, so maybe that caused it. The glowplug one's been there forever. From what I understand, there's a known issue on these cars with the glowplug wiring loom?

 

Car runs fine, a little rough when cold on a cold morning, but to be expected from an old diesel with no working glowplugs. Drives fine, gets 60mpg. Just puts the light on because of the MAF.

 

6 Faults Found:
000258 - Mass Air Flow Sensor (G70) 
               P0102 - 000 - Signal too Low
             Freeze Frame:
                    Fault Status: 01110000
                    Fault Priority: 0
                    Fault Frequency: 1
                    Reset counter: 255
                    Mileage: 296523 km
                    Time Indication: 0
                    Date: 2000.00.00
                    Time: 19:06:50

             Freeze Frame:
                    RPM: 798 /min
                    Speed: 0.0 km/h
                    Load: 0.0 %
                    Duty Cycle: 64.7 %
                    Bin. Bits: 00101000
                    Mass Air / Rev.: 240.0 mg/str
                    Mass Air / Rev.: 0.0 mg/str

005658 - Glowplug for Cylinder 1 (Q10) 
               P161A - 000 - Open Circuit
             Freeze Frame:
                    Fault Status: 01110000
                    Fault Priority: 0
                    Fault Frequency: 1
                    Reset counter: 255
                    Mileage: 297394 km
                    Time Indication: 0
                    Date: 2000.00.00
                    Time: 08:55:50

             Freeze Frame:
                    RPM: 903 /min
                    Speed: 0.0 km/h
                    Load: 0.0 %
                    Voltage: 14.21 V
                    Bin. Bits: 00101000
                    Temperature: 14.4°C
                    Bin. Bits: 10110000

005659 - Glowplug for Cylinder 2 (Q11) 
               P161B - 000 - Open Circuit
             Freeze Frame:
                    Fault Status: 01110000
                    Fault Priority: 0
                    Fault Frequency: 1
                    Reset counter: 255
                    Mileage: 297394 km
                    Time Indication: 0
                    Date: 2000.00.00
                    Time: 08:55:50

             Freeze Frame:
                    RPM: 903 /min
                    Speed: 0.0 km/h
                    Load: 0.0 %
                    Voltage: 14.21 V
                    Bin. Bits: 00101000
                    Temperature: 14.4°C
                    Bin. Bits: 10110000

005660 - Glowplug for Cylinder 3 (Q12) 
               P161C - 000 - Open Circuit
             Freeze Frame:
                    Fault Status: 01110000
                    Fault Priority: 0
                    Fault Frequency: 1
                    Reset counter: 255
                    Mileage: 297394 km
                    Time Indication: 0
                    Date: 2000.00.00
                    Time: 08:55:50

             Freeze Frame:
                    RPM: 903 /min
                    Speed: 0.0 km/h
                    Load: 0.0 %
                    Voltage: 14.21 V
                    Bin. Bits: 00101000
                    Temperature: 14.4°C
                    Bin. Bits: 10110000

005661 - Glowplug for Cylinder 4 (Q13) 
               P161D - 000 - Open Circuit
             Freeze Frame:
                    Fault Status: 01110000
                    Fault Priority: 0
                    Fault Frequency: 1
                    Reset counter: 255
                    Mileage: 297394 km
                    Time Indication: 0
                    Date: 2000.00.00
                    Time: 08:55:50

             Freeze Frame:
                    RPM: 903 /min
                    Speed: 0.0 km/h
                    Load: 0.0 %
                    Voltage: 14.21 V
                    Bin. Bits: 00101000
                    Temperature: 14.4°C
                    Bin. Bits: 10110000

000564 - Boost Pressure Regulation 
               P0234 - 000 - Limit Exceeded (Overboost Condition) - Intermittent
             Freeze Frame:
                    Fault Status: 00110000
                    Fault Priority: 0
                    Fault Frequency: 1
                    Reset counter: 255
                    Mileage: 304814 km
                    Time Indication: 0
                    Date: 2000.00.00
                    Time: 12:13:33

             Freeze Frame:
                    RPM: 3045 /min
                    Speed: 88.0 km/h
                    Load: 83.1 %
                    Voltage: 14.52 V
                    Bin. Bits: 10101000
                    Absolute Pres.: 2029.8 mbar
                    Absolute Pres.: 2346.0 mbar

Readiness: 1 1 0 0 1 
 

Engine code and year and I'll tell you what wires go where and what fuse to check.

Thanks @WinoIt's a 2008, can't think what the engine code is off hand, will check in daylight and come back to you. I'll bleep-check all the fuses in the morning just to be sure, but I think I did that when I bought it. 

Looks like the same whether it's BJB, BXE or BLS. (Cabin) Fuse 29 feeds pin 2 of MAF through a black/green wire; that fuse also feeds a crankcase ventilation heater on some cars, which sometimes fail short circuit. So if it's blown and re-pops, find and unplug that heater.

3 to ECU pin 60 green

4 to ECU pin40 black/violet

5 to ECU 82 black

 

Edited 11 October, 20214 yr by Wino

Thanks for that - BXE rings a bell, it's not BJB (just because I know it's different to our old Caddy). 

 

So (after fuses) in the first instance, I'm looking for a straight 12v down pin 2?

 

I'm just wondering if it's 3,4 or 5 that's not going through, if that coincides with the glowplug fault at a multiplug or if they go straight back the ECU?

Edited 11 October, 20214 yr by StevesTruck

Ignition switched 12V, yes.

3,4,5 all direct to ECU. 

Another recent post had glowplug errors as well as MAF fault that mysteriously vanished when MAF was sorted, don't understand how, but you never know. 😀

So, the AFM wasn't getting power, so I bodged a temp feed to it. The car ran rough for a few seconds then settled down.

 

Checked the fuses, blew my tiny mind on the left to right mirror because the diagram's for a left hand drive. Got set right by Nige - big thanks for that.

 

Stuck a fuse in 29 (didn't have one). Drove down the lane, the fault light went off and stayed off for my ten minute drive home. 

 

I haven't had chance to scan it again, but I've got a couple of hundred miles to do tomorrow, so we'll see what catches fire between now and me getting home. 

I'm nowhere I can check the value of that fuse just now, 10 amp rings a bell?

Take a spare with you tomorrow, and try to locate that heater connection just in case. 

40 minutes ago, Wino said:

I'm nowhere I can check the value of that fuse just now, 10 amp rings a bell?

 

It should be 10amp

 

The diagrams show the ventilation heater as only fitted with "optional equipment " ??

Thanks for that Nige, yeah, no idea what that equipment may be. 

Any idea on location?

44 minutes ago, Wino said:

Thanks for that Nige, yeah, no idea what that equipment may be. 

Any idea on location?

 

I searched the whole of the engine section in ElsaWin and no mention of the heater or even the ventilation system 

 

As to the optional equipment, I'm wondering if it could be a cold climate option ??

The heater if fitted is in the pipe from the top of the rocker/cam cover to the inlet pipe to the turbo

Edited 15 October, 20214 yr by nige8021

 

Confirms it's a cold climate option 👍

So, it wasn't that simple....

 

Drove it to Nottingham yesterday. 

When I went to come back, the engine light was back on. 

Drove back fine apart from one little sort of flat, misfirey moment between 5th and 6th.

Rough to start this morning.

Then as I was going up hill a few minutes from the house, it misfired then cut out, wouldn't restart, or would restart briefly while the pedal was down. 

Pulled the AFM plug, no different.

Pulled the fuse out (none blown), no different. 

Managed to get it started and drive it briefly, but as soon as you come off the pedal, it cuts out. 

 

Starting to work round things that I could roadside with the very basics.

 

Throttle stepper is actuating fine and looks clean. 

Smokes when it's cranking but not starting, so I'll say it's getting fuel.

 

Just waiting for recovery to drop it off, then I'll try and get some fault codes and live data at least. 

So, none starter at the minute, so I couldn't get a proper read, but I did a little live data while I was cracking it over...

 

No fault codes from the engine, but like I say, none-starter.

MAF showed data, seemed to move about a bit as the engine had a splutter.

Throttle pedal sensor's working fine.

Throttle position sensor is saying 100% all the time, even which the throttle body cycles as I prime the ignition and then turn it back off.

 

Is that TPS figure normal? Is there a lonk between AFM and TPS?

 

Turned out to be a massive coincidence.

 

I changed the air flow meter, and the lift pump died a day later