Volkswagen Touran - P148B Adblue heater fault

Adam Owner/Technician Glasgow, United Kingdom Posted   Latest   Edited   Bounty  
Engine Mil Active

Vehicle details:

  • Make/Model: Volkswagen/Touran
  • Engine: 1.6 L
  • Fuel: Diesel
  • Year: 2016
  • BHP: 115
  • Engine Code: DGDA
  • Sales type 5T132Z
  • VIN: WVGZZZ1TZHW016732

This car came to us with an active engine MIL and two permanent DTCs (did NOT clear on request):

9650 - Output Module 2 for Heating of Reductant

P148C 00 [175] - Malfunction

9654 - Output Module 1 for Heating of Reductant

P148B 00 [175] - Malfunction

We have replaced the following: 

  • Adblue tank (contains heater - a repair kit is NOT available for this vehicle's reductant system)
  • Adblue heating control unit

Following installation of the above, initially both permanent DTCs cleared out fine (for the first time - happy days), but following an extended road test after refilling system and adapting learned values for SCR system (as per VAG manual), one of the two DTCs has returned and will NOT clear out (P148B/9654 - Output Module 1 for Heating of Reductant - Malfunction). With reference to the manufacturer's circuit diagram, it looks like "output module 1" relates to the in-tank heater, as it is labelled as "Z102 - Heater for reducing agent tank (heater circuit 1)". This logical assumption, however, an assumption none the less. There is an additional Adblue heater in the system: part of one of the pipes "Reducing agent line with heater".

We have carried out following additional testing:

  • Confirmed Adblue heating control unit power/ground okay
  • Confirmed wiring power/ground to from Adblue heating control unit to heater elements okay
  • Confirmed electrical integrity of heater elements okay (ohms check at component connectors: both in-tank heater and line heater ~2.2 Ohms)

I'm really hoping for some assistance with this one gents. I'm wondering if there is a followup process that needs to be completed (as tank replaced)...or something. I'm struggling to maintain a logical path on this one.

Thanks in advance guys, appreciate it!

EDIT: I'm looking at the circuit diagram again and I'm thinking maybe connector block or something (affecting the control side of things on the heater module) has maybe suffered water damage and there is a corrosion/volt drop at the connector...The recurring DTC description doesn't refer to the "output" side, after all. Just that there is a "malfunction". Perhaps on the input side. This connecter block is my next check.

Doru Technician
Suceava, Romania
Doru Default

Unplug the heater from the pipe that goes to the injector and see the error code; it will appear immediately, You don't even have to start the car (regarding the assumption). Is the tank you bought new? I ask because usually the tank heater error appears after an extended road test .

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Adam Owner/Technician
Glasgow, United Kingdom
Adam Default

Thanks - I did all this - believe it or not, the DTC doesn't behave that way for simple identification purposes.

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Caleb Diagnostician
Mishawaka, Indiana
Caleb Default

Do you have ODIS or a scanner that you can bidirectionally command the heaters with?? If so throw an amp clamp around each heater and see if ohms law can help you nail this thing!!

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Eric Owner/Technician
Edgerton, Wisconsin
Eric Default

Have you looked up the code set criteria for the P148B/9654 code? I found it listed in an older (2014) vehicle and it described it as, Current still flowing above 200 ua when the heater is turned off. I'm not sure it is the same for your vehicle but I doubt VW would change it over a couple of years. If the above code set criteria is correct then you have a heater stuck on. A sticking relay or…

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Adam Owner/Technician
Glasgow, United Kingdom
Adam Resolution

**UPDATE: Fixed** It was the indeed the connector block, located in driver's footwell. Volt-drop removed > Sorted. Many thanks all. PS - Can I award bounty to all contributors?

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Khalifah Engineer
Kampala, Uganda
Khalifah Default

Hey guys am stuck with a certain w204 (271)kompressor Benz this car does not communicate with any diagionostic chine I have checked all the fuses am ok when I try to daigonise it shows that the ecm and the gcm are not equipped I hav tried to search for the gateway I hav failed to see it or wat can I do with it

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Off Topic
Caleb Diagnostician
Mishawaka, Indiana
Caleb Default

You need to post this as a post in Diag​.​net

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