Limp Mode (again) Plus many other issues...

[Coach Pat]

2002 Golf TDI.
List of fault codes:
P0671-674 Cyl. 1 thru 4 glow plug circuit
P0402 EGR FLOW EXCESSIVE DETECTED
P0128 COOLANT THERMOSTAT BELOW REGULATING TEMP (is that really a bad thing??)
P1556 No DTC definition found.
I've reviewed the VTN post. I will start there to address the limp mode issue. Question is this: Are any or all of the other faults related? P0671 thru 674 I believe may be a harness issue (as I was told from the dealer).
Old Blue has 150,000 + miles and still averaging 43 mpg ~ 2.32 gal/100 miles.

Any information is greatly appreciated.

[Keithuk]

Welcome to the forum.

VAG Error Code: 17055
EOBD II Error Code: P0671

Fault Location:
Glow Plug Cylinder 1 (Q10) Circuit - Circuit malfunction

Possible Cause:
No Pre-Glow Period.
Poor Cold Starting.

Glow Plug Wiring faulty.
Poor connection.
Relay.
Glow plug control module.
Glow Plug faulty.
Engine control module (ECM).

Possible Solutions:
Check Glow Plug Wiring.
Check Glow Plug.

Special Notes:
See TDIClub Glow Plug 101


VAG Error Code: 16786
EOBD II Error Code: P0402

Fault Location:
Exhaust gas recirculation (EGR) system - Excessive flow detected

Possible Cause:
Malfunction Indicator Light (MIL) ON.
Reduced Exhaust Gas Recirculation (EGR).
Reduced Power Output/Engine running rough.
Increased Emissions.

Hose leak/blockage.
Basic setting not carried out.
Exhaust Gas Recirculation (EGR) Flow restricted/clogged.
Exhaust Gas Recirculation (EGR) Valve stuck closed/leaking/faulty.
Wiring and/or Connector(s) from/to Exhaust Gas Recirculation (EGR) Valve faulty.
Exhaust Gas Recirculation (EGR) System faulty.

Possible Solutions:
Check/Clean Exhaust Gas Recirculation (EGR) System.
Check/Replace Exhaust Gas Recirculation (EGR) Valve.
Check Wiring and/or Connector(s) from/to Exhaust Gas Recirculation (EGR) Valve.


VAG Error Code: 16512
EOBD II Error Code: P0128

Fault Location:
Coolant thermostat - Coolant temperature below thermostat regulating temperature

Possible Cause:
Mechanical fault.


VAG Error Code: 17964
EOBD II Error Code: P1556

Fault Location:
Charge Pressure Control - Negative deviation

Possible Cause:
Reduced power output.
Limp mode.

Boost Pressure too Low.
Hoses/Pipes incorrect connected, disconnected or leaking.
Charger Pressure Control defective.
Variable Nozzle Turbo (VNT) nozzles stuck.
Solenoid Valve for Boost Pressure Control (N75) defective.

Possible Solutions:
Check Hoses/Pipes to/between Components.
Check Solenoid Valve for Boost Pressure Control (N75).
Check / Clean / Replace Charge Pressure Control.
Check / Clean mechanism for variable nozzles.

As taken from my Free EOBD II Error Codes software

[Coach Pat]

Thank you for the response.

I tried PB on the VTN lever last night per the VTN guide. Unfortunately that was not the quick fix I was hoping it to be. Looks like I'll be under the hood this weekend.
Thank you again for the guidance. I'll report back.