P20C7Reductant Heater D Control Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P20C7 reports that heater D's control circuit is grounded or overloaded with current. Only Deutz publishes the code: for its downstream line heater (SPN 520471) it maps to FMI 4, a voltage that is too low or a short to a low source. No vehicle maker documents thresholds for heater D. GM's tables for heaters 1–3 show the usual method, comparing the output voltage with the heater off against a low band and the current with it on, then setting Type A, set after a 2 s window; Ford uses 15 A on its two heater circuits. CARB requires such output circuits to be monitored for shorts that contradict what the module has commanded. Look for chafing on the line harness, water in a connector or an element with an internal short. Open and high counterparts are P20C5 and P20C8, the performance test is P20C6.
- What you may notice
- Warning lamp, possibly with a blown fuse
- Unheated downstream line and delayed dosing in frost
- Likely causes
- LikelyHeater D wire chafed through to ground
- PossibleWater in the heater D connector
- RareInternal short inside the heated downstream line
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €60 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.