1998 jetta P0605

cheezed2meet

New member
Joined
Jan 25, 2023
Location
oregon
TDI
1998 jetta
hello all,
so I picked up a couple 98 jetta's. one had a check engine light when I got it, I have a vagcom, reading the codes, it was a glow plug code, I replaced glow plugs and harness, code is gone, but a new code appeared after maybe 10 miles of driving. P0605, which is a ROM error in the ecm. when driving, on accel from dead stop, its sluggish in first gear up until about 1500rpm, then has plenty of power and accels fine through rest of gears. this is my first ahu tdi, so I am no expert on them. I also discovered a connector on the passenger side with the wires broken from the connector and touching each other, ??possibly intake manifold temp sensor??, could the wires touching have shorted something in the ecm? what should my next move be to figure out my issue?
 

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
Hey
Have you gone through and conducted all the maintenance that's probably not been done over the years? Air / fuel filter etc etc? I wouldn't run it all that long until you get the timing belt done, it's never safe when you don't know when that was last done. Five years or 60k miles, which ever comes first.

You didn't mention how many miles are on these either...that would be good to know.

You'd have to figure out exactly what sensor has the bad connection in order to know whether it affects the ECU. A photo of the sensor showing where it's located would help.

Steve
 

Rig

Veteran Member
Joined
Apr 14, 2010
Location
New Mexico
TDI
1998 Jetta TDI, 210k miles
I also discovered a connector on the passenger side with the wires broken from the connector and touching each other, ??
I would post some pictures if you can, would be good to see the condition of the car, miles etc...The intake air temperature sensor should be in the middle of the engine bay on the hose leading to your intake manifold. It's unlikely the problem, but it wouldn't hurt to clean your sensors. What you are describing sounds more like the N75 (which probably needs replacement) or the MAF sensor plug which can get unplugged even it looks like its plugged in (although this will probably give you a CEL)

The MAF sensor can be problematic and might need cleaning, which is likely if the air filter is dirty. This alone can cause limp mode in my experience. Get some sensor cleaner or MAF cleaner spray, open up your air intake and spray the sensor off.

N75: https://www.idparts.com/ahu-n75-valve-028906283f-721895550-p-451.html

But yes, replace your ECU hose: https://www.myturbodiesel.com/d2/1000q/a3b4/ecu-hose-chip-tdi-65535.htm

And buy a new relay 109: https://www.idparts.com/relay-109-a4b4a3-1j0906381a-1008300003-p-350.html

Otherwise, the usual stuff, oil change, air filter, timing belt, battery. When I got my Jetta the vacuum hose to ECU did indeed need to be replaced, in fact it would be a good idea to replace ALL the vacuum lines and fuel return lines between the injectors.

common how tos:

new owner checklist:
 
Last edited:

cheezed2meet

New member
Joined
Jan 25, 2023
Location
oregon
TDI
1998 jetta
sorry for the late response all, been very busy with work. its a high mile car, something like 270k miles. this past weekend, I removed the ecm and took a look inside, the vacuum line inside had a hole in it. replaced it, cleared code, and still has not come back. will try to get a picture of the connector that broken, so I can get some advice on what sensor it is. i already did maintenance, oil change, fuel filter, new brakes and brake fluid. previous owner said timing belt was done within a few thousand miles, I inspected the belt, it looks good, no cracks or signs of rotting. also, noticed when its warm, it goes into first gear really hard, and the clutch pedal feels very light. should I check for air in system or for bad fluid? or expect to replace clutch.

thanks everyone
 

Abacus

That helpful B4 guy
Joined
Nov 10, 2007
Location
Relocated from Maine to Dewey, AZ
TDI
Only the B4V left
“High mileage”…lol! Sorry, but that’s not high at all.
What is the date code on the timing belt tensioner?

Since you changed the brake fluid, did you also do the clutch slave, since it uses the same reservoir? It’s very easy to do.
 

Rig

Veteran Member
Joined
Apr 14, 2010
Location
New Mexico
TDI
1998 Jetta TDI, 210k miles
“High mileage”…lol! Sorry, but that’s not high at all.
Haha, not for the engine, but its long enough to accrue some issues elsewhere lol.

@cheezed2meet make sure to change the brake fluid every 2 years, seriously. Otherwise it will ruin your clutch/slave cylinders which can semi strand you. Happened to me twice and to my uncles B4. Not something that people regularly mention for maintenance but important.
 

ToddA1

Top Post Dawg
Joined
Aug 3, 2011
Location
NJ 08002
TDI
'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
2 years may be the recommended, but how many of us truly follow this interval? I’m guilty of it on the wagen, and I’ve yet to see failure due to moisture in the system.

-Todd
 
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