P2748 — Intermediate Shaft Speed Sensor “B” Circuit Intermittent #

Note: The exact wording of this code may vary depending on the vehicle manufacturer (OEM).

• Intermediate Shaft Speed Sensor “B” Circuit Intermittent (General, most OEMs)
• Intermediate Shaft Speed Sensor “B” Intermittent/Erratic Signal (Chrysler)
• Intermediate Shaft Speed Sensor “B” Circuit Range/Performance (GM, variation)
• Transmission Intermediate Shaft Speed Sensor “B” Circuit Intermittent (Toyota, Lexus)

Summary of Code P2748 #

P2748 is an OBD-II diagnostic trouble code (DTC) that indicates the transmission control module (TCM) has detected an intermittent electrical issue in the circuit for the Intermediate Shaft Speed Sensor “B”. This sensor measures the rotational speed of a shaft inside the transmission and provides vital data for shifting and torque converter operation. When the circuit signal is unreliable—dropping out sporadically—the TCM cannot accurately manage gear changes or monitor transmission performance. This code is most commonly associated with automatic transmissions and can affect drivability and safety if left unresolved. Fast, accurate diagnosis is essential to prevent further transmission or driveline damage.

Frequent Symptoms for Code P2748 #

Drivers may notice a variety of performance and shifting issues when code P2748 is active. Since the transmission relies on intermediate shaft speed data for shift timing and torque management, any interruption can cause noticeable drivability concerns. Typical symptoms include:

• Harsh or delayed shifting (especially between 2nd and 3rd gears)
• Transmission stuck in limp or fail-safe mode
• Erratic speedometer readings (in some vehicles)
• Check Engine Light (MIL) illuminated
• Reduced acceleration or poor fuel economy

Probable Causes for Code P2748 #

The P2748 code is most often triggered by electrical issues affecting the intermediate shaft speed sensor “B” or its circuit. Less commonly, mechanical failures within the transmission can also lead to this code. Below are the most frequent causes, ranked by likelihood:

1. Faulty intermediate shaft speed sensor “B” (internal electronic failure or intermittent open/short)
2. Damaged or corroded sensor wiring or connectors (loose pins, water ingress, or chafed wires)
3. Poor electrical ground or voltage supply to the sensor
4. TCM (Transmission Control Module) issues (rare, but possible if all else checks out)
5. Internal transmission mechanical issues (such as worn shaft or excessive endplay impacting sensor signal)

Step-by-Step Diagnosis for Code P2748 #

A systematic approach is key when diagnosing P2748. The goal is to confirm the fault, isolate the root cause, and avoid unnecessary parts replacement. Here’s how a skilled technician would proceed:

• 1. Scan and document all transmission-related codes. Clear codes and road test to see if P2748 returns.
• 2. Inspect sensor wiring and connectors visually. Look for corrosion, damaged insulation, or loose pins at the sensor and TCM.
• 3. Check intermediate shaft speed sensor “B” with a multimeter. Test for correct resistance (per OEM specs) and ensure there is no open or short circuit.
• 4. Backprobe sensor signal while wiggling harness. Use a lab scope or voltmeter to detect intermittent signal dropouts during movement.
• 5. Verify sensor power supply and ground integrity. Confirm voltage and ground are present at the sensor connector.
• 6. Inspect for transmission internal issues if wiring and sensor check out. This may require removal of the transmission pan (or further disassembly) for mechanical inspection.
• 7. As a last resort, test or replace the TCM. Only if all other steps have failed to resolve the issue.

Possible Repairs for Code P2748 #

Repairing code P2748 depends on the diagnosed root cause. The following fixes directly address the most common sources:

• Replace the intermediate shaft speed sensor “B”. Most frequent and cost-effective repair.
• Repair or replace damaged wiring/connectors. This includes removing corrosion, fixing chafed wires, or replacing broken connector housings.
• Restore proper ground or power supply. This could involve repairing a broken ground strap or fixing a blown fuse in the sensor circuit.
• Reprogram or replace the TCM. Only if confirmed faulty after all other diagnostics.
• Repair internal transmission components. (e.g., worn intermediate shaft or sensor reluctor ring) if a mechanical root cause is found.

Can You Drive with Code P2748? #

Driving with code P2748 is NOT recommended for extended periods. While a vehicle may still operate, the transmission can enter limp mode, causing poor performance or even preventing gear changes. Prolonged driving may result in additional transmission damage or create unsafe driving conditions. If you notice severe shifting issues or warning lights, schedule diagnostic and repair service as soon as possible.

Vehicles Most Commonly Affected by Code P2748 #

While P2748 can appear on a wide range of vehicles equipped with electronically controlled automatic transmissions, it is most frequently reported on models from these manufacturers:

• Chrysler, Dodge, Jeep (especially with 62TE and 68RFE transmissions)
• General Motors (GM) (select models with 6L80/90 or 8-speed autos)
• Toyota/Lexus (various models with U-series transmissions)
• Ford (less common, but possible in some 6F35/6F50 units)
• Honda/Acura (rare, but possible on certain V6 automatics)

Common Mistakes & Best Practices for Code P2748 #

When dealing with intermittent electrical codes like P2748, technicians and DIYers often make missteps that can lead to misdiagnosis or wasted time. Here are typical pitfalls and pro tips:

• Replacing the sensor without checking wiring/connectors first.
• Ignoring intermittent faults because the code “goes away.” Intermittent means it can return and cause bigger issues later.
• Overlooking TSBs (Technical Service Bulletins) or known OEM issues. Some manufacturers have bulletins for connector or harness upgrades.
• Neglecting to clear codes and verify repair with a thorough test drive.
• Failing to use proper diagnostic equipment (multimeter, oscilloscope) to confirm circuit integrity.

Express FAQ for Code P2748 #

Q: Can I fix code P2748 myself?
A: If you’re comfortable with basic electrical diagnostics and have access to a multimeter, you can check wiring and replace the sensor. However, intermittent faults can be challenging; a professional diagnosis is recommended if the code persists.

Q: Is code P2748 covered under my transmission warranty?
A: If your vehicle is still under manufacturer powertrain warranty, sensor and wiring repairs related to P2748 are often covered. Always check with your dealer or OEM for specific coverage.