B0515 – RH Heater Discharge Temp Sensor Failure

System: Body | Standard: ISO/SAE Controlled | Fault type: General

Definition source: SAE J2012/J2012DA (industry standard)

DTC B0515 indicates the control module has detected a failure associated with the right-hand (RH) heater discharge temperature sensor. This sensor feedback is used by the body-related climate control logic to judge discharge air temperature and adjust doors, blower strategy, or heater output as designed. Because HVAC architectures, sensor locations, and diagnostic monitors vary by vehicle, the exact conditions that set B0515 (and the exact symptom set) can differ between platforms. Always confirm the monitored circuit type, connector views, pinouts, and test specifications using the applicable service information before performing electrical testing or replacing parts.

What Does B0515 Mean?

B0515 means the module has identified a failure with the RH heater discharge temperature sensor. Based strictly on the official definition, this DTC is tied to the sensor input used to represent discharge air temperature on the right-hand side of the heater/HVAC air distribution. SAE J2012 defines the overall structure of DTCs, but the meaning of this specific code is governed by its official title/description: a failure of the RH heater discharge temperature sensor circuit/input as detected by the module’s built-in monitoring.

Quick Reference

• Subsystem: RH heater discharge air temperature sensing circuit (HVAC discharge temperature feedback, Body system).
• Common triggers: Sensor signal missing/implausible, intermittent connection, poor terminal fit, damaged wiring near HVAC case, or sensor element fault.
• Likely root-cause buckets: Wiring/connector issues, sensor failure, power/ground/reference problems (as applicable), control module input fault (less common).
• Severity: Usually comfort-related; may reduce temperature regulation accuracy or cause HVAC to default to a fallback strategy.
• First checks: Verify code status (current/history), inspect RH discharge sensor connector and harness routing, look for loose pins/corrosion, and compare RH discharge temp reading to other HVAC temperature readings in live data.
• Common mistakes: Replacing the sensor without checking connector pin fit or harness damage; ignoring intermittent faults that only occur with vibration or temperature changes.

Theory of Operation

The RH heater discharge temperature sensor is typically a thermistor-style device whose resistance changes with air temperature. A control module (varies by vehicle: HVAC control head or a body control module that manages HVAC inputs) interprets the sensor signal through a reference/signal/ground arrangement or a similar input circuit design. The module uses the resulting temperature estimate to help regulate right-side discharge temperature by adjusting air mix and airflow control elements.

The module monitors this input for validity. A fault may be flagged if the signal is missing, stuck, intermittently dropping out, or does not behave as expected compared with other available HVAC temperature-related inputs. When the monitor fails, the module may substitute a default value, limit right-side temperature control, or store B0515 as a current or history DTC depending on how long the condition is present.

Symptoms

• Inaccurate temperature: RH vents blow warmer or cooler than the selected setting.
• Temperature imbalance: Noticeable difference between left and right discharge temperatures during similar settings.
• HVAC fallback: System may default to a conservative air-mix strategy to protect comfort control logic.
• Intermittent operation: Symptoms come and go with bumps, vibration, or after the cabin heats/cools.
• Indicator message: HVAC-related warning/message may appear depending on vehicle configuration.
• Stored DTC: B0515 present as current or history without strong driveability impact.

Common Causes

• Loose, corroded, backed-out, or damaged connector terminals at the RH heater discharge temperature sensor
• Wiring harness damage (chafing, pinched section, heat damage) causing an open circuit or an unintended short between conductors
• High resistance in the sensor signal or return circuit due to poor splice integrity or partially broken wire strands
• Loss of sensor reference supply or sensor ground/return (varies by vehicle design) from an upstream wiring or junction issue
• RH heater discharge temperature sensor internal fault (sensor element drift, internal open, or intermittent internal connection)
• Water intrusion or contamination at the sensor or in-line connector leading to unstable signal readings
• HVAC control module or body control module input fault (less common; confirm all external circuit checks first)
• Incorrectly seated sensor after HVAC service, or harness routed incorrectly and stressed by HVAC housing movement

Diagnosis Steps

Tools that help: a scan tool that can read body/HVAC DTCs and data parameters, a digital multimeter, and basic back-probing tools. A wiring diagram and connector end views from service information are strongly recommended because sensor wiring (reference, signal, and return) varies by vehicle. If available, use a breakout lead to avoid terminal damage during testing.

1. Confirm the DTC is present and recorded as current versus history. Record freeze-frame or environmental data if available (ambient temperature, HVAC settings, engine state), then clear the code and see if it resets under similar conditions.
2. Use the scan tool to view live data for the RH heater discharge temperature sensor (name varies by vehicle). Look for readings that are implausible for the current conditions, stuck (no change), or erratic (jumping). If the parameter is unavailable, note that the fault may still be present but not exposed as a PID on some platforms.
3. Perform a focused visual inspection of the RH heater discharge temperature sensor area. Check that the sensor is fully seated, the connector lock is engaged, and the harness is not stretched, pinched, or routed against sharp edges or hot components.
4. Inspect the sensor connector and module-side connector(s) involved (varies by vehicle). Look for corrosion, moisture, bent pins, spread terminals, and evidence of fretting. Repair terminal issues before deeper electrical testing.
5. With the system powered as specified in service information, check for the presence of the proper reference supply and ground/return at the sensor connector (architecture varies). If reference or ground/return is missing, trace upstream to the next connector or splice and isolate where it is lost.
6. Check the sensor signal circuit for an open or short. With the sensor disconnected, verify continuity end-to-end from the sensor connector to the receiving module pin, and verify there is no unintended continuity to ground or to power on the signal conductor. Repeat the same checks on the return/ground conductor if the design uses a dedicated sensor return.
7. Perform a wiggle test while monitoring live data and/or the multimeter. Manipulate the harness near the sensor, along known rub points, and at connectors. If the reading drops out, spikes, or the DTC sets during movement, isolate the exact segment causing the intermittent.
8. Do voltage-drop testing on the sensor ground/return and on the reference feed under operating conditions (as applicable). Excessive drop indicates resistance in connectors, splices, or wiring that may not be obvious during static continuity checks.
9. If wiring checks pass, evaluate the sensor itself per service information. Depending on design, this may include verifying the sensor’s response to temperature change (for example, comparing readings at different HVAC operating states) and confirming the signal changes smoothly rather than stepping or dropping out.
10. If the sensor and circuit test good but the code persists, verify the module input is receiving the expected signal at the module connector (back-probe carefully). If the signal is correct at the module pins while the module reports a fault, follow service information for module-level diagnostics (including checks for shared references/grounds and network-related faults if applicable).

Professional tip: When the issue is intermittent, prioritize testing methods that load the circuit. A circuit can pass a simple continuity check yet fail under vibration or current flow. Combine live-data logging with a controlled wiggle test and voltage-drop checks at the same time to quickly distinguish a sensor fault from a high-resistance connection or a partially broken conductor.

Possible Fixes & Repair Costs

Repair costs for B0515 vary widely by vehicle because access to the HVAC case, harness routing, and required calibration steps differ. The final cost depends on confirming the root cause (sensor vs wiring vs module), parts needed, and labor time.

• Repair or replace damaged wiring to the RH heater discharge temperature sensor circuit after verifying the fault with testing
• Clean, reseat, or replace loose/corroded terminals at the sensor connector and the HVAC control module connector (as applicable)
• Replace the RH heater discharge temperature sensor if it fails resistance/signal checks per service information
• Restore correct power supply and ground integrity to the HVAC control module or sensor circuit if voltage-drop testing shows excessive loss
• Repair harness chafing or pinched sections near HVAC housing, dash supports, or pass-throughs where movement can create intermittent opens
• Perform required relearn/initialization procedures (varies by vehicle) after component or module service
• Update or reprogram the controlling module only if service information and testing support a software-related fault

Can I Still Drive With B0515?

In most cases, you can still drive with B0515 because it is a body/HVAC-related fault, but cabin comfort and window defogging performance may be reduced or inconsistent. Use caution if visibility is affected by poor defrost/defog operation. If the vehicle shows additional warnings related to braking, steering, reduced power, stalling, or no-start conditions, do not drive and diagnose those issues first.

What Happens If You Ignore B0515?

Ignoring B0515 can lead to ongoing incorrect HVAC temperature control on the right-hand side, inconsistent air discharge temperature, and reduced defrost/defog effectiveness under certain conditions. An intermittent electrical fault may worsen over time due to vibration, moisture intrusion, or terminal fretting, potentially adding more HVAC-related DTCs.

Last updated: March 19, 2026

Vehicles Commonly Affected by B0515

• Vehicles equipped with dual-zone or multi-zone automatic climate control
• Vehicles that use discharge air temperature sensors integrated into the HVAC air distribution system
• Vehicles with HVAC components packaged tightly behind the instrument panel (higher risk of harness strain)
• Vehicles operated in high-humidity or high-dust environments that can accelerate connector contamination
• Vehicles with a history of interior repairs, dash removal, or HVAC case service (higher chance of disturbed connectors)
• Vehicles exposed to frequent vibration or rough-road use that can aggravate intermittent terminal contact
• Vehicles with prior water intrusion events affecting footwells or under-dash wiring
• Vehicles with aftermarket electrical accessories installed near HVAC wiring (routing/connection risks vary by vehicle)