P0128 - please help! 05 TDI Beetle

11155 Views 5 Replies 6 Participants Last post by turboturbo, Jul 14, 2014

Brdbuss

Discussion Starter · May 17, 2014

I purchased this for my daughter with about 79,000 miles on it. Within a month, CEL came on and code P0128 came up. With help from this forum, I replaced the coolant temp sensor...thanks! A couple of months later, the code came back. With further help here, I drained the radiator and replaced the thermostat and refilled with G12 and h2o. Now, about 2 months later, code is back. Coolant level is good, red indicator has never illuminated, my daughter rarely drives on the highway, usually about 10 miles per day. Both the coolant temp sensor and thermostat were purchased from the vw dealership (still paying on those loans. Wow what a racket). Any ideas or help will be greatly appreciated.

Save

1 - 6 of 6 Posts

janitz

· #2 · May 17, 2014

Faulty wiring could cause this, check for the obvious first and see if the plug at the wire end has corroded.

I ran into a corroded wire while working on my AC last year, wasted so much time and money trying to fix other parts when all I needed to do was pull the plug and sand off the corrosion.

Save

nightpicnic

· #3 · Jul 7, 2014

janitz said:
Faulty wiring could cause this, check for the obvious first and see if the plug at the wire end has corroded.

I ran into a corroded wire while working on my AC last year, wasted so much time and money trying to fix other parts when all I needed to do was pull the plug and sand off the corrosion.

Definitely check the wiring, that could likely be the cause.
I've heard that the ECTs on these beetles are a common problem. I also heard that VW came out with an updated ECT senor, I would make sure that they installed the updated sensor when you had it repaired at the dealership.

Save

Lew

· #4 · Jul 7, 2014

Pull the connector on the reservoir where you added the G12. Make sure it is not wet inside where the connector plugs in. Sometime this area can be wet from a leak coming from the reservoir around the electrical prongs. That's why some have done what is called a coolant migration mod. A small hole is drilled in the lower part of the connection port so if any water might be seeping into that area it will drain away. This may not be your problem, but it's worth checking.

Save

billymade

· #5 · Jul 14, 2014

ENGINE-CODES OBDII CODE LIST P0128 VOLKSWAGEN
P0128 Volkswagen

P0128 Volkswagen - Coolant Temperature Below Operating Range

Possible causes
- Leaking or stuck open thermostat
- Low engine coolant level
- Insufficient warm up time
- Faulty engine coolant temperature sensor
- Engine coolant temperature sensor harness is open or shorted
- Engine coolant temperature sensor circuit poor electrical connection
What does this mean?
Tech notes
If cooling system is not leaking and the fluid level is OK, replacing the thermostat usually takes care of the problem.
What does this mean?
When is the code detected?
The engine coolant temperature does not reach to specified temperature even though the engine has run long enough.
Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
P0128 Volkswagen Description
Indicates that the thermostat monitor has not achieved the required engine operating temperature within a specified amount of time after starting the engine.

See less See more

Save

turboturbo

· #6 · Jul 14, 2014

Get a scanner on it and find out your actual operating temperature. Until that is done, you're just guessing. Warmed up, it should be running at minimum 85C. It's entirely likely that you need another thermostat.

Save

1 - 6 of 6 Posts

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.

Top Contributors this Month