Code
P1435
FIAT
P — Powertrain
Additive dosing system fault
Views:
UK: 4
EN: 11
RU: 7
AI status
Completed
Completed
100%
Causes
- Empty or low additive tank
- Clogged dosing lines, filters or nozzle
- Failed dosing pump or motor
- Stuck or leaking dosing valve/injector
- Faulty additive level/temperature/pressure sensor
- Wiring harness damage, corrosion or poor connector connection
Symptoms
- Malfunction Indicator Lamp (MIL) / warning light illuminated
- Additive level or system fault message on dash
- DPF regeneration inhibited or failed
- Poor cold-start emissions or increased emission readings
- Reduced engine power or limp mode in some vehicles
- Unusual noise from dosing pump area
What to check
- Read and record stored DTCs and freeze-frame data with a capable scan tool
- Check additive tank level and visually inspect for contamination/crystals
- Visually inspect wiring, connectors and earth points for corrosion, damage or water ingress
- Check fuses and relays feeding the dosing pump/system
- Perform basic power/ground check at dosing pump and sensors (voltage and ground)
- Check for blockages: inspect dosing line, filter and dosing nozzle
Signal parameters
- Additive tank level sensor: voltage or resistance values and plausibility
- Pump supply voltage (key on and while commanded) and ground continuity
- Pump current draw (mA/A) while commanded — high or zero indicates problem
- Dosing valve/actuator: command duty cycle or PWM and measured response
- Injector/nozzle flow/pressure if applicable
- Temperature sensor values for additive (plausibility)
Diagnostic algorithm
- Connect a diagnostic scanner and record all active and history fault codes and freeze-frame data
- Verify additive tank level and top up with the correct fluid if low; inspect for contamination
- Perform a visual inspection of dosing pump, lines, filters, dosing nozzle, sensors and connectors for damage, crystallisation or leaks
- Check fuses/relays and supply voltage at the dosing pump connector (key on, engine off and when commanded)
- Command the dosing pump/valve with the scan tool and observe pump current and any flow from nozzle (use proper safety PPE and containment for fluid)
- If pump does not run but has supply voltage, test pump current draw and continuity; replace pump if mechanical failure suspected
- If pump runs but no flow, inspect or replace in-line filters and clean/replace dosing nozzle
- Check level/temperature/pressure sensor signals for plausibility and perform resistance/voltage checks against manufacturer data
- Inspect and test wiring harness for opens/shorts and poor grounds; repair as needed
- Clear codes after repairs and perform regeneration/test drive to confirm fault does not return; if persistent, consider module-level diagnosis or consult manufacturer service bulletins
Likely causes
- Additive tank empty or low
- Dosing pump electrical supply fault (fuse/relay/connector)
- Clogged dosing filter/line or blocked dosing nozzle
- Dosing pump mechanical failure or seized motor
- Faulty additive level or pump current sensor
Fault status
Status
Additive dosing system fault detected. MIL illuminated and dosing may be disabled. Inspect additive level, pump, lines, sensors and electrical supply.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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