P20AE — Reductant Metering Unit Temperature Sensor Circuit Low

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How to diagnose with an OBD scanner

  1. Read the code and freeze frame Connect an OBD2 scanner, confirm P20AE is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
  2. Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
  3. Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the reductant metering unit temperature sensor for damage, corrosion, chafing or poor contact.
  4. Subsystem check Check for supply voltage at the reductant metering unit temperature sensor connector first; then measure resistance from the signal wire to ground — near-zero ohms confirms a short to ground in the harness.
  5. Subsystem check Measure reference voltage, ground and signal continuity at the component connector.
  6. Subsystem check Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
  7. Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P20AE does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P20AE (parts and labor, USD, independent shop rates): Control module repair: $300–$1,000; Repair wiring or connectors: $80–$250; Replace the faulty sensor or actuator: $150–$500. Overall, fixing P20AE usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

How much does it cost to fix P20AE?

Control module repair — $300–$1,000; Repair wiring or connectors — $80–$250; Replace the faulty sensor or actuator — $150–$500. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

How do I diagnose P20AE myself?

Start with a scan: confirm P20AE, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the reductant metering unit temperature sensor, and verify the suspect component against live data before buying parts.

Is it safe to drive with P20AE?

In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

What are the symptoms of P20AE?

Drivers most often notice: the affected system operates intermittently or not at all, increased fuel consumption in some cases, Check Engine Light on, possible limp mode depending on the affected component.

What is the most common cause of P20AE?

The most common causes are: corroded, loose or damaged connector, open or shorted wiring in the circuit, control module driver fault.

What does P20AE mean?

P20AE (Reductant Metering Unit Temperature Sensor Circuit Low) is stored when self-diagnostics detect abnormal readings or behaviour of the sensor and actuator circuits. It belongs to the powertrain (engine/transmission) category.

“Circuit low” means the voltage on the reductant metering unit temperature sensor circuit stays below the expected minimum — close to ground. The usual physical reasons are a short to ground, a chafed wire touching metal, a missing supply voltage, or a failed component dragging the signal down.

The module monitors this system continuously while driving. When readings fall outside the expected range for a defined number of drive cycles, it stores P20AE and switches on the warning light. Freeze frame data saved with the code shows the exact conditions — rpm, load, temperature, speed — at the moment the fault was detected, which is the best starting point for diagnosis.

What causes P20AE?

  • signal wire shorted to ground (chafed insulation)
  • missing supply voltage to the reductant metering unit temperature sensor
  • failed reductant metering unit temperature sensor pulling the signal low
  • corroded, loose or damaged connector
  • control module driver fault
  • blown fuse feeding the circuit
  • faulty sensor or actuator of the affected circuit

Common symptoms of P20AE

  • the affected system operates intermittently or not at all
  • increased fuel consumption in some cases
  • Check Engine Light on
  • possible limp mode depending on the affected component

How to diagnose P20AE

  1. Connect an OBD2 scanner, confirm P20AE is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
  2. Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
  3. Visually inspect the wiring harness and connectors related to the reductant metering unit temperature sensor for damage, corrosion, chafing or poor contact.
  4. Check for supply voltage at the reductant metering unit temperature sensor connector first; then measure resistance from the signal wire to ground — near-zero ohms confirms a short to ground in the harness.
  5. Measure reference voltage, ground and signal continuity at the component connector.
  6. Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
  7. Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P20AE does not return.

How to fix P20AE

Start with the cheapest and most common causes before replacing expensive parts:

  • Control module repair — $300–$1,000
  • Repair wiring or connectors — $80–$250
  • Replace the faulty sensor or actuator — $150–$500

How much does it cost to fix P20AE?

Repair cost depends on which component actually failed. Typical scenarios for P20AE (parts and labor, USD, independent shop rates):

  • Control module repair: $300–$1,000
  • Repair wiring or connectors: $80–$250
  • Replace the faulty sensor or actuator: $150–$500

Overall, fixing P20AE usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Can you drive with P20AE?

In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

Related OBD2 codes