Technical Diesel Help! Code P069749 sensor supply 3- internal electrons failure

[Chip2026]

Hi looking for some help, I had a blocked dpf I removed the dpf off the van to clean it as it was really blocked but I had no warning lights to tell me it was blocked strange? The only fault code I had was p069749 sensor 3 internally electronics failure. I have found out that the DPF pressure sensor is giving no reading on live data 0v the same for the DPF temp sensor 0v no reading. I have replaced all sensors with new ones and still no readings also if there unplugged it never stores a fault code which I find strange. Any help is appreciated as I know the dpf will block again if I continue driving when there’s no reading as it won’t regenerate.

 

[Mike1alike]

If the DPF pressure sensor and temperature sensor both show 0 V in live data, and unplugging them does not generate a fault code, that usually points to a power supply or wiring issue, not bad sensors.
Both sensors require a 5 V reference and ground from the ECU. If the 5 V reference line is missing, all sensors on that circuit will read 0 V and the ECU cannot read them.
Things to check:
️ 1. 5 V reference at the sensor connectors
With ignition ON, measure between the 5 V supply pin and ground.
You should see about 5 V.
️ 2. Sensor ground
Check continuity between the sensor ground pin and chassis ground.
Should be near 0 Ω.
️ 3. Wiring harness
On Ducato these wires run close to the exhaust and DPF, so melted or damaged wiring is not uncommon.
️ 4. Shared sensor circuit
The MAP sensor / boost sensor / DPF sensors may share the same 5 V reference line.
If one sensor or wire is shorted, it can pull the whole circuit down.
️ 5. Engine bay fuse box / ECU supply
If the 5 V reference is missing at multiple sensors, check ECU power feeds and grounds.

Since you already replaced the sensors, the next step is definitely checking for the 5 V supply and ground at the connectors. Without that, the ECU cannot read the sensors and DPF regeneration will never occur.

 

[Chip2026]

If the DPF pressure sensor and temperature sensor both show 0 V in live data, and unplugging them does not generate a fault code, that usually points to a power supply or wiring issue, not bad sensors.
Both sensors require a 5 V reference and ground from the ECU. If the 5 V reference line is missing, all sensors on that circuit will read 0 V and the ECU cannot read them.
Things to check:
️ 1. 5 V reference at the sensor connectors
With ignition ON, measure between the 5 V supply pin and ground.
You should see about 5 V.
️ 2. Sensor ground
Check continuity between the sensor ground pin and chassis ground.
Should be near 0 Ω.
️ 3. Wiring harness
On Ducato these wires run close to the exhaust and DPF, so melted or damaged wiring is not uncommon.
️ 4. Shared sensor circuit
The MAP sensor / boost sensor / DPF sensors may share the same 5 V reference line.
If one sensor or wire is shorted, it can pull the whole circuit down.
️ 5. Engine bay fuse box / ECU supply
If the 5 V reference is missing at multiple sensors, check ECU power feeds and grounds.

Since you already replaced the sensors, the next step is definitely checking for the 5 V supply and ground at the connectors. Without that, the ECU cannot read the sensors and DPF regeneration will never occur.

Hi thanks for your reply, I have checked the above and all readings are as they should be when the sensor is plugged in ground 0v signal 0.5v and supply 5v. Ground pin continuity is 0.07/0.08

Still pretty lost what it could be. The only other thing is could it be my alternator it is slightly whining but it still charges ok at just over 14v

Is it still possible it could be another sensor that’s not allowing me to calibrate the new dpf sensor or showing any live data to all dpf sensors. Like EGR maf map ect