A 2011 Land Rover Discovery IV rolled into the bay with a check engine light and a dashboard countdown warning that the vehicle would soon refuse to start. The technician pulled four codes: P2BAE, P2BAF, P2BA9, and U0241.
Unpacking the SCR Countdown
When an L319 platform triggers a no-start countdown, I know the engine control module has decided the exhaust emissions are no longer meeting legal requirements. This active restriction is called driver inducement. The codes give us a specific map of why the system is unhappy.
DTC
Description
P2BAE
NOx Exceedance
P2BAF
Driver Inducement
P2BA9
DEF Quality
U0241
Lost Communication with Headlamp Control Module A
The first three codes are highly interconnected. P2BAE and P2BAF indicate that NOx levels are too high and the driver inducement is active. P2BA9 points a finger directly at the Diesel Exhaust Fluid quality.
Pinpointing the Exhaust Fault
The diagnostic platform we build analyzed this combination and ranked a defective NOx sensor as the most likely culprit at 90 percent. These sensors sit in a high heat and vibration environment. When they fail, they send constant or erratic values to the ECM, making the system think the AdBlue system has failed. The specific reference data points to sensor part FPLA-5J299-BB 0281006779/780. The immediate diagnostic step is to monitor the NOx sensor live data and visually inspect the wiring harness for damage.
If the sensor checks out, the next probability is contaminated or degraded AdBlue fluid at 80 percent. Poor DEF quality prevents the SCR catalytic converter from neutralizing nitrogen oxides. Testing involves checking the tank for crystallization or contamination, flushing it with fresh ISO 22241 DEF, and resetting the SCR Quality Monitor.
The system also flagged a clogged AdBlue dosing injector at 75 percent probability. Urea crystallizes easily. A clogged nozzle means the exhaust does not receive enough DEF to reduce the NOx, triggering the exact same exceedance codes even if the fluid in the tank is perfect.
The Isolated Network Code
The final code, U0241, has nothing to do with the exhaust. It means the powertrain control module lost communication with headlamp control module A over the CAN bus. This is a known issue for the L319 architecture, frequently caused by water ingress into the headlamp housing or wiring damage. Since the customer did not report lighting issues, this is likely an intermittent electrical fault requiring a continuity test of the CAN lines between the body control module and the headlamp module.
Approach This Diagnosis
Always tackle the no-start countdown first to get the vehicle moving again. Verify the NOx sensor live data before you spend time draining the DEF tank or tearing down the dosing injector. Have you seen this specific combination of SCR codes on the Discovery IV?
