Ford Transit SCR Fault P20BD Stored
Being dealership based you would assume that we have all the information required to successfully diagnose and repair vehicles and in some cases this is true, however, with SCR concerns the diagnostic information seems to be playing catch up, leaving us just like an independent garage and using system knowledge and traditional testing methods to successfully diagnose and fix concerns.
The vehicle in question was 2018 Ford Transit 350 Tipper with the 2.0 Ecoblue engine, unlike the 2.2 engine, this system does not have its own dedicated SCR control unit. The vehicle had just the engine warning light on (no SCR warning) and no reported symptoms or lack of power.
Using Ford IDS I scanned the vehicle and found a permanent fault code stored P20BD.
P20BD: Reductant Heater "B" Control Circuit / Open.
A straight forward enough fault code stored when the "self test" returns a higher than expected (open circuit) resistance on the heater circuit, in this case heater "B". Knowing the concern, the next part of the diagnosis was to consult the wiring diagram for this vehicle, deducing there where two heater circuits, one for the reductant pressure line and one for the main tank. Neither where identified as A or B nor 1 or 2. However, both controlled via the glow plug module. Thinking smart and knowing the glow plug module is in an easy location, I thought it would be easier to test here, rather than raise the vehicle on a ramp and access the SCR tank assembly, by testing at the disconnected multi-plug of the glow plug module.
Using a simple resistance test on the multi-meter between the control wire and a good ground, I located heater "B" as being the reductant pressure line heater, having a resistance reading of over 125kOhm. The other circuit having approx. 5 ohms. This test did not however rule out the possibility of a wiring issue and served mainly to identify the circuit.
With the vehicle now lifted, testing of the heater direct at the two-pin multi-plug gave a value of approx. 125kOhm. To confirm the diagnosis a substitute value of 4 ohms was placed across the connector pins of the vehicle harness using a decade box. After deleting the fault code and starting the engine, the fault code did not return as it previously did.
Knowing the diagnosis was correct and proven, a new reductant pressure line can now ordered and fitted.
Please subscrive to SY Diagnostics youtube, LINK