B0189 – Solar Load Sensor #2 Circuit Range (sunload)

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

Definition source: SAE J2012/J2012DA (industry standard)

DTC B0189 indicates the body control system has detected a range-related fault in the Solar Load Sensor #2 circuit (sunload). In plain terms, the control module expected the sensor signal to behave within an anticipated operating window and to change in a believable way as sunlight conditions change, but it did not. A “circuit range” DTC is about signal plausibility and response, not automatically a short or open. The exact enable criteria, fail conditions, and the way the vehicle reports or reacts to this DTC can vary by vehicle, so confirm connector locations, pinouts, and test specifications using the appropriate service information before condemning parts.

What Does B0189 Mean?

B0189 – Solar Load Sensor #2 Circuit Range (sunload) means the vehicle has detected that the Solar Load Sensor #2 circuit signal is outside the expected range or is not performing plausibly for current conditions. The code’s focus is the circuit’s measured behavior (how the signal tracks sunlight load) rather than a guaranteed component failure. SAE J2012 defines how DTCs are structured and categorized, but the specific diagnostic thresholds, comparison logic (if any), and how long the fault must be present before setting B0189 are determined by the vehicle’s control strategy and should be verified in service information.

Quick Reference

• Subsystem: Solar load (sunload) sensing circuit for Solar Load Sensor #2 in the body system (typically used for automatic climate/load compensation).
• Common triggers: Signal that is implausible for ambient light conditions, signal that changes too slowly/erratically, skewed reading compared with expected operating behavior, or intermittent circuit issues that distort the sensor output.
• Likely root-cause buckets: Wiring/connector integrity, sensor element degradation or contamination, reference/power/ground quality to the sensor, poor terminal fit/pin drag, or a module input issue (less common).
• Severity: Usually low for immediate safety; may affect comfort functions and automatic control accuracy. Other body or HVAC-related DTCs may increase urgency.
• First checks: Confirm DTC is current, inspect sensor area for obstruction/contamination, check connectors/terminals, verify stable power/ground/reference at the sensor, and review live data for plausibility.
• Common mistakes: Replacing the sensor without checking power/ground quality, ignoring intermittent connector issues, or misreading “range” as a guaranteed short/open instead of a plausibility/performance problem.

Theory of Operation

A solar load sensor measures incident sunlight so the body/climate control logic can adjust cabin temperature control and airflow based on radiant heat. Depending on vehicle design, Solar Load Sensor #2 may be a second sensing element or an additional sensor used for comparison or coverage. The sensor typically produces an electrical signal that changes as sunlight intensity changes, and the control module interprets that signal as “sunload.”

For a circuit range/performance decision, the module looks for a believable signal within an expected operating window and expects the reading to respond appropriately when sunlight changes. B0189 can set when the signal appears stuck, biased high/low relative to what the module deems plausible, changes too slowly, becomes erratic due to intermittent connection issues, or does not correlate with related operating context. Exact criteria and comparisons vary by vehicle.

Symptoms

• Auto HVAC inconsistency: Automatic temperature control may overcool or undercool in bright sun compared to shaded conditions.
• Comfort fluctuations: Cabin comfort may drift after sun exposure changes (entering shade/garage) with delayed or incorrect compensation.
• Indicator lamp: A warning indicator for body/HVAC-related faults may illuminate, depending on platform strategy.
• Stored code: B0189 may be stored as current or history, sometimes returning after clearing if conditions repeat.
• Intermittent behavior: Symptoms may come and go with vibration, temperature changes, or after interior work near the sensor or harness.
• Related HVAC behavior: Automatic blower, discharge temperature, or mode decisions may seem less accurate than normal.

Common Causes

• Damaged wiring in the Solar Load Sensor #2 signal circuit (chafing, pinched harness, internal conductor damage)
• Connector issues at the sensor or control module (loose fit, backed-out terminals, corrosion, contamination)
• High resistance in power or ground feeds shared with the sensor (poor splice, weakened terminal tension, partially broken wire)
• Poor ground integrity causing a skewed or unstable sensor reading (ground point looseness, corrosion, stacked grounds)
• Solar Load Sensor #2 fault or signal drift (sensor output out of expected range for current conditions, slow response)
• Sensor mounting/location issues affecting reading consistency (misalignment, obstruction, damaged housing); exact design varies by vehicle
• Intermittent open/short that only appears with vibration, heat, or steering-column/dash movement
• Control module input/circuit fault or software/calibration issue (less common; verify all circuits first)

Diagnosis Steps

Tools that help include a scan tool capable of reading body DTCs and live data, a digital multimeter for continuity and voltage-drop checks, and basic backprobing supplies. A wiring diagram and service information are important because sensor pinouts, shared power/grounds, and enabling conditions vary by vehicle. If available, use a data logger function to capture intermittent range faults during changing light conditions.

1. Confirm B0189 is active or stored, record freeze-frame or environment data (if available), and check for related body/HVAC DTCs that could indicate shared power/ground or network issues.
2. Clear the code and perform a short verification drive or functional check while observing the Solar Load Sensor #2 parameter in live data. Note whether the signal appears stuck, erratic, or slow to respond to changing light.
3. Visually inspect the Solar Load Sensor #2 area and harness routing. Look for a cracked sensor lens/housing, obstruction over the sensing area, signs of prior dash work, and harness pinching or rubbing near brackets or sharp edges.
4. Inspect the sensor connector and module-side connector for terminal damage: corrosion, moisture, bent pins, pushed-out terminals, and poor pin fit. Reseat connectors and ensure locking tabs fully engage.
5. With the ignition in the appropriate state per service information, check the sensor’s power and ground circuits. Use voltage-drop testing on the ground path under load (not just continuity) to find resistance that can skew the signal and trigger a range fault.
6. Check the signal circuit for opens/shorts and high resistance. Perform end-to-end continuity checks (sensor to module), then a loaded test where possible, since a circuit can pass continuity yet fail under current due to poor terminal contact.
7. Perform a wiggle test while monitoring the live sensor value and/or DMM readings: gently move the harness at the sensor, along the dash routing, and near the module connector. If the value jumps or drops out, isolate the exact movement point and inspect that section for an intermittent connection.
8. Compare plausibility with related inputs (varies by vehicle), such as another solar load sensor channel or ambient light-related data, if those parameters are available. A consistent mismatch supports a circuit/sensor skew rather than a single momentary event.
9. If wiring and connector integrity checks pass, verify the sensor’s response behavior: observe live data during gradual changes in light and during transitions (shade to sun). A sensor that is consistently biased, slow, or intermittently flat-lined may be out of range even with good wiring.
10. If the sensor is suspected, substitute with a known-good sensor only after confirming power/ground/signal integrity. After replacement, clear codes and repeat the same monitoring conditions to confirm the fault does not return.
11. If the issue persists with verified circuits and a verified-good sensor, follow service information for module input testing, pin-fit checks at the module, and any required configuration or relearn steps. Consider module fault only after all circuit/sensor checks are proven.

Professional tip: Range faults can be intermittent and condition-dependent, so prioritize data logging. Capture Solar Load Sensor #2 live data while driving through alternating shade/sun and over bumps, then correlate any dropouts with harness movement points. If the value changes abruptly when connectors are touched or the dash harness is flexed, treat it as a connection/terminal issue first, even if static continuity tests look normal.

Possible Fixes & Repair Costs

Repair costs for B0189 vary widely because the fault is a circuit range issue that can stem from wiring, connector condition, sensor output plausibility, or module interpretation. The final cost depends on confirmed test results, parts required, and labor time to access and verify the circuit.

• Clean and reseat connectors at the Solar Load Sensor #2 and the receiving module; address any bent, spread, or backed-out terminals found during inspection.
• Repair wiring faults by fixing opens, shorts between conductors, or high-resistance sections; restore proper routing and protection if harness damage is found.
• Restore power and ground integrity by correcting poor grounds, loose fasteners, corrosion, or excessive voltage drop on the sensor feed/return circuits (verify with voltage-drop testing).
• Replace Solar Load Sensor #2 only after confirming the circuit is intact and the sensor signal remains implausible or nonresponsive during controlled lighting changes and live-data review (varies by vehicle).
• Address mounting/placement issues if the sensor is loose, obstructed, or improperly seated in its location, causing erratic or skewed readings that fail plausibility checks.
• Update or reconfigure the control module only if service information calls for it and all circuit/sensor checks pass; verify that the correct variant/coding is present where applicable.

Can I Still Drive With B0189?

In most cases, you can usually drive with B0189 because it is a body-system circuit range fault related to Solar Load Sensor #2 and typically affects automatic climate/comfort behavior rather than core drivability. However, if other warnings appear or you notice electrical issues such as multiple body faults, intermittent instrument cluster behavior, or any braking/steering warnings, avoid driving and diagnose promptly. Expect the HVAC system to potentially respond incorrectly to sunlight changes until the fault is fixed.

What Happens If You Ignore B0189?

Ignoring B0189 can lead to ongoing incorrect or inconsistent automatic HVAC performance, such as poor temperature regulation during changing sunlight conditions, and may contribute to customer complaints and increased cabin discomfort. If the underlying cause is a wiring or connector problem, it may worsen over time, potentially causing additional circuit faults, intermittent behavior, or more frequent warning indicators depending on how the networked body modules validate sensor plausibility.

Last updated: March 18, 2026

Vehicles Commonly Affected by B0189

• Vehicles with automatic climate control that uses a sunload input to adjust HVAC output
• Vehicles equipped with multiple sunload sensors or dual-zone systems that reference more than one solar load input
• Vehicles with dashboard-top sensor locations where heat, glare, and handling can stress connectors and wiring
• Vehicles frequently parked outdoors where temperature cycling can aggravate marginal terminal tension and connector sealing
• Vehicles with recent windshield/dashboard service where sensor connectors or harness routing may have been disturbed (varies by vehicle)
• Vehicles with interior electrical modifications that may affect power/ground quality or harness integrity
• Higher-mileage vehicles where vibration and aging increase the likelihood of intermittent contact and high resistance
• Vehicles operated in humid or corrosive environments where connector oxidation can skew signals

For the most accurate next step on your vehicle, compare scan-tool live data to the service information test procedure for the Solar Load Sensor #2 circuit range check and confirm results with wiring and voltage-drop tests.