B0748 – D (drive) Indicator Circuit High (BCM)

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

Definition source: SAE J2012/J2012DA (industry standard)

DTC B0748 indicates the Body Control Module (BCM) detected a “Circuit High” condition in the D (drive) indicator circuit. In practical terms, the BCM is seeing the D indicator input or feedback at a higher-than-expected electrical level for the current operating state. This is an electrical diagnosis (high input/short-to-power/open ground) rather than a confirmed mechanical problem. Because indicator circuit designs and monitoring logic vary by vehicle, the exact circuit path (cluster lamp driver, PRNDL display, selector assembly input, or networked message verification) and the exact enabling conditions can differ. Always confirm the specific circuit routing, connector locations, and test specifications in the appropriate service information before concluding a root cause.

What Does B0748 Mean?

B0748 means the BCM has detected a high electrical signal condition in the D (drive) indicator circuit. The official definition is “D (drive) Indicator Circuit High (BCM),” which identifies both the affected function (the D/Drive indicator) and the module reporting the fault (BCM). In SAE J2012 terms, “Circuit High” corresponds to a signal that is above the expected range, commonly caused by a short to power, an open or high-resistance ground/return path, incorrect feed voltage, or an internal driver/input issue. The code does not, by itself, prove the indicator component has failed; it only confirms the BCM observed a high-input fault condition under its monitoring criteria.

Quick Reference

• Subsystem: D (drive) gear position indicator circuit monitored by the BCM (indicator lamp/PRNDL display path varies by vehicle).
• Common triggers: Short-to-power on the indicator control/signal line, open ground/return, connector terminal spread or corrosion, or incorrect power feed to the indicator circuit.
• Likely root-cause buckets: Wiring/connector issues, indicator assembly or instrument cluster circuitry, power/ground distribution faults, BCM input/driver fault (less common), configuration/software (where applicable).
• Severity: Typically low to moderate; may cause incorrect gear indication and driver confusion, which can become a safety concern depending on operating conditions.
• First checks: Verify the complaint, scan for related BCM/cluster/transmission-range codes, inspect connectors at the selector/cluster/BCM for damage, and check for obvious harness chafing near moving components.
• Common mistakes: Replacing the indicator/cluster or BCM without confirming a high-input condition with circuit testing and without checking for shorts to power or poor grounds.

Theory of Operation

The D (drive) indicator is the driver-facing confirmation of the selected drive range. Depending on vehicle design, the BCM may directly drive an indicator lamp, command a display in the instrument cluster, or interpret a signal from a range/selector assembly and then control the indicator output. The circuit may be a discrete input to the BCM, a discrete output from the BCM, or a combination of an input plus a controlled output to the cluster.

For a “Circuit High” fault, the BCM detects that the monitored circuit remains electrically high when it should be low or within an expected window. This can happen if the signal/control wire is shorted to a power source, if the ground/return side is open causing the circuit to float high, if a connector or terminal fit creates unintended feedback, or if the indicator driver/input stage is malfunctioning. The BCM typically sets the code after the condition is present for a calibrated time and may also store freeze-frame or status data to help pinpoint when it occurred.

Symptoms

• Incorrect indication: D (drive) indicator stays on at the wrong time or appears when another range is selected.
• No/erratic indication: D indicator may flicker, behave inconsistently, or fail to respond to range changes.
• Warning message: Cluster may display a gear indicator warning or general body/indicator fault message (varies by vehicle).
• Related codes: Additional BCM/instrument cluster codes may set if the indicator circuit fault affects other monitored outputs.
• Intermittent behavior: Symptoms may worsen with vibration, steering column/console movement, or temperature changes if a harness/terminal issue is present.
• Backlighting anomalies: Other indicator lights or PRNDL segments may glow faintly due to unintended voltage backfeed (design-dependent).

Common Causes

• Short-to-power in the D (drive) indicator control/signal circuit (including a chafed harness contacting a battery feed or another powered circuit)
• Open ground path or high resistance in the indicator’s ground circuit, causing the BCM to interpret the circuit as stuck high
• Connector issues at the indicator, shifter assembly, cluster/display interface, or BCM (backed-out terminals, poor pin fit, corrosion, moisture intrusion)
• Incorrectly routed, pinched, or damaged harness near moving components (shifter linkage/console area) leading to intermittent high input
• Internal fault in the D (drive) indicator lamp/LED/module (varies by vehicle design) creating an abnormal high signal condition
• BCM power/ground concern affecting input biasing or circuit interpretation (shared grounds, poor ground eyelet, loose fastener)
• Aftermarket accessory/remote start/alarm wiring interaction with indicator/shift-related circuits (splices, taps, shared grounds)
• BCM internal fault or calibration/logic issue (consider only after external circuit integrity is proven)

Diagnosis Steps

Tools typically needed: a scan tool capable of reading BCM DTCs and body data parameters, a digital multimeter, and service information with wiring diagrams and connector views. A backprobe kit, test light (where appropriate), and basic hand tools help with connector checks. If available, use a breakout lead to reduce terminal damage during testing and to support wiggle testing.

1. Confirm the complaint and scope. Verify the DTC is stored in the BCM and record freeze frame/environmental data and any companion body or communication DTCs. Clear the code and see if it resets immediately or only under certain conditions.
2. Check indicator operation and related functions. Observe whether the D (drive) indicator is stuck on, stuck off, flickers, or behaves opposite of the selected range. Note whether other range/indicator positions show abnormal behavior, as this can suggest shared power/ground or a harness issue (varies by vehicle).
3. Use live data to identify the monitored parameter. In the BCM data list, locate the parameter associated with the D (drive) indicator circuit or status (naming varies by vehicle). Log the parameter while shifting through ranges (with the vehicle secured). A “stuck high” reading that does not respond to commands/position changes supports a circuit-high condition.
4. Perform a visual inspection of the most likely harness areas. Inspect the wiring from the shifter/console area to the dash/BCM routing points. Look for chafing, pinched sections, prior repairs, loose connectors, and signs of moisture or contamination at connectors.
5. Wiggle test with data logging. With the scan tool logging the relevant BCM parameter and/or DTC status, gently wiggle harness sections and connectors at the indicator, shifter assembly, intermediate connectors, and BCM connector. If the status toggles or the DTC sets during movement, focus on that segment for pin fit, broken strands, or intermittent short-to-power.
6. Connector and terminal integrity checks. Key off, disconnect the suspected connectors (indicator/shifter interface and BCM as applicable). Inspect for backed-out terminals, spread terminals, corrosion, and damaged seals. Verify terminal tension using appropriate methods from service information; repair pin fit issues rather than forcing pins.
7. Check for short-to-power on the signal/control circuit. With the circuit disconnected at both ends when possible (to isolate modules), use a multimeter to test whether the indicator signal/control wire shows continuity to battery feed circuits or shows voltage present when it should be isolated. If voltage is present with modules disconnected, trace for harness contact with a powered source.
8. Verify ground integrity with voltage-drop testing. If the circuit uses a dedicated ground (varies by vehicle), load the circuit as directed by service information and perform voltage-drop testing across the ground path (from the component ground to the chassis/ground point). Excessive drop indicates resistance in the ground path that can bias the circuit high; repair the ground connection or wiring as needed.
9. Verify power and reference feeds affecting the circuit. Check the BCM power and ground supplies and any shared feeds to the indicator/shifter interface. A poor BCM ground or shared ground can distort circuit biasing and cause a high-input interpretation. Confirm all related fuses and power distribution points are correct and secure.
10. Component isolation test (varies by design). If the indicator is a separate lamp/LED/module or part of an assembly, isolate it from the harness and observe whether the circuit-high condition persists with the component unplugged. If the BCM still reports high with the component disconnected, suspect a harness short-to-power or BCM-side issue. If the condition disappears, suspect the component or its immediate connector.
11. BCM evaluation as a last step. After confirming wiring integrity, connector health, and proper power/ground, consider BCM internal fault or logic/calibration concerns. Reconfirm by repeating the isolation tests and ensuring no external circuit can force the input high. Follow service information for any module test routines, reconfiguration, or replacement requirements.

Professional tip: A circuit-high DTC is often intermittent and load-dependent. When you find a suspect connector or harness area, reproduce the fault while monitoring live data and simultaneously measuring the circuit with a meter. Correlating the scan tool’s “stuck high” status with a measured unwanted voltage or a ground voltage-drop under load is the fastest way to prove whether you have a short-to-power, an open/weak ground, or a module-side interpretation issue.

Possible Fixes & Repair Costs

Repair costs for B0748 can vary widely because the root cause may be as simple as a connector issue or as involved as circuit repair and module-level diagnosis. Labor time depends on circuit access, confirmation testing, and whether additional faults are present.

• Repair damaged wiring in the D (drive) indicator circuit, including chafed insulation or short-to-power conditions found during testing
• Clean, reseat, or replace affected connectors/terminals (poor pin fit, corrosion, or backed-out terminals) and verify proper terminal tension
• Correct power/ground distribution issues that bias the indicator signal high (restore proper ground path, repair shared ground splice, or correct misrouted power feed as verified)
• Replace the D (drive) indicator lamp/LED assembly or the indicator driver component if testing confirms an internal short or incorrect high output behavior (varies by vehicle design)
• Repair the instrument cluster or indicator interface circuit if it is proven to be forcing the circuit high or loading the BCM output incorrectly (varies by vehicle)
• Reprogram, reset, or replace the BCM only after all external circuit faults are ruled out and module-side output/input testing confirms BCM involvement

Can I Still Drive With B0748?

Usually, B0748 affects the D (drive) indicator status rather than core drivetrain operation, so the vehicle may still be drivable. However, do not rely on the indicator for gear confirmation until the fault is fixed. If you also have warnings related to shifting behavior, brake/steering systems, reduced power, no-start, or the transmission range display is unreliable, treat it as a safety risk and avoid driving until verified with service information and testing.

What Happens If You Ignore B0748?

Ignoring B0748 can leave you with an inaccurate or stuck D (drive) indicator, increasing the chance of gear selection confusion and related safety issues. The underlying circuit fault may worsen over time (intermittent becomes constant), potentially creating additional BCM electrical faults, draining diagnostic time later, and complicating inspection/repair if the short-to-power spreads to shared harness sections.

Last updated: March 20, 2026

Vehicles Commonly Affected by B0748

• Vehicles with a BCM-controlled gear position indicator lamp or integrated cluster indicator logic
• Vehicles using an LED-based PRNDL/gear indicator with electronic drivers instead of direct bulb power
• Platforms where the instrument cluster communicates gear/indicator status via a body network while still using discrete indicator circuits (varies by design)
• Vehicles with console-mounted shifter indicator assemblies connected to the BCM through a dedicated harness
• Vehicles with prior interior, console, or cluster service where connectors may be partially seated or pinched
• Vehicles operated in high-humidity or contamination-prone environments where terminals can corrode
• Vehicles with modified/added electrical accessories that may introduce unintended power feeds into body circuits
• Vehicles with harness routing near sharp brackets or moving components that can chafe wiring over time

After repairs, clear the code and verify B0748 does not return under the same operating conditions that originally triggered the high circuit detection.