P0748 Code: Pressure Control Solenoid A Electrical
The TCM detected an electrical fault (open, short or wrong current) in pressure control solenoid A's circuit.
At a glance
Severity: Moderate
- Meaning
- Pressure Control Solenoid A Electrical
- System
- Transmission · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $80–$1,600
- DIY difficulty
- Moderate
Pressure control solenoids are driven with a controlled current rather than simply switched on and off, and the TCM measures that current continuously. P0748 sets when the measured current or voltage in the solenoid A circuit is impossible for a healthy circuit: an open coil, a short to ground or power, or a resistance far from specification. Because the TCM can no longer control pressure precisely, most transmissions fall back to a safe default – often maximum line pressure, sometimes combined with limp mode in a fixed gear. That's why the typical complaint is hard engagements and firm, banging shifts. On GM's 4L60E and 4L65E, P0748 is one of the classic codes, with the solenoid reachable after removing the pan and filter.
Can I keep driving? The car can usually be driven to a shop, but hard shifts load the drivetrain mounts, U-joints and the transmission itself. If it's stuck in one gear, keep to moderate speeds and avoid highways where the engine would over-rev.
How to read P0748
- P Powertrain
- 0 Generic (SAE)
- 7 Transmission
- 48 Specific fault
Symptoms
- Harsh engagement when shifting into Drive or Reverse
- Firm, banging upshifts and downshifts
- Limp mode with a single fixed gear on many vehicles
- Transmission warning message in the instrument cluster
- Code appearing after rain, washing or driving through water
- Check engine light, sometimes with other solenoid codes
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Solenoid coil open or shorted internally
- Damaged wiring or corroded, loose connector pins
- Internal transmission harness or pass-through connector fault
- TCM/PCM driver circuit failure
- Low battery voltage or poor ground
- Wrong or poor-quality replacement solenoid, or connector left unplugged after service
- Blown fuse feeding the transmission solenoids
Diagnosis step by step
Read current data
Compare commanded and actual pressure control solenoid current in the scan data. Actual current stuck at zero suggests an open circuit; current pinned high or a driver fault flag suggests a short.
Tools: OBD-II scanner
Measure solenoid resistance
Measure across solenoid A through the transmission connector. Variable-force pressure solenoids are low-resistance, often around 3–8 ohms depending on design; 'OL' means open, and a reading near zero means a short.
Tools: Multimeter
Split internal from external wiring
If the reading at the case connector is wrong, the fault is inside the transmission – the solenoid or internal harness. If it's right there but wrong at the TCM connector, repair the vehicle harness between them.
Tools: Multimeter
Check for shorts to ground
With both connectors unplugged, check each solenoid wire to ground and to battery voltage. There should be no continuity to ground and no voltage on the wires.
Tools: Multimeter
Check power supply and grounds
Confirm battery voltage of about 12.6 V resting and 13.5–14.8 V running, a good fuse on the solenoid feed, and clean ground connections for the TCM. Low supply voltage can make the TCM misjudge solenoid current.
Tools: Multimeter
Replace and relearn
After replacing the solenoid, harness or TCM, clear codes and reset adaptive values. Drive through all gears gently so the TCM can relearn shift pressures.
Tools: OBD-II scanner
Where the parts are
- 1Battery
- 2Alternator
- 3Engine computer (ECM)
- 4CAN bus
- 5Transmission
- 6Wheel speed sensor
- 7High-voltage battery
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Repair wiring or clean and reseat connector | Yes | $80–$300 |
| Replace pressure control solenoid (pan-accessible) | No | $250–$650 |
| Replace internal harness or pass-through connector | No | $300–$800 |
| Replace solenoid pack or valve body with integrated solenoids | No | $600–$1,600 |
| Replace and program TCM/PCM | No | $500–$1,300 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Chevrolet
On Silverado, Tahoe and other GM trucks with the 4L60E or 4L65E, P0748 is a common code. The pressure control solenoid sits on the valve body behind the pan and filter; check the internal harness and connector while you're there, as they can crack with age.
Field data
| Kia | 3 | Sorento, Spectra |
|---|
Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.
Emissions / smog test impact
Will fail
A stored P0748 turns on the check engine light, which fails OBD emissions testing. Clear it after the repair and complete the readiness monitors before retesting.
Frequently asked questions
Why does the transmission bang into gear with P0748?
When the TCM loses electrical control of pressure solenoid A, most designs default to high line pressure. Clutches then apply hard, which feels harsh but prevents slipping and burning.
How is P0748 different from P0746?
P0748 is an electrical fault in the solenoid circuit, such as an open or short. P0746 means the circuit is electrically fine, but the pressure doesn't respond as commanded, usually because the valve is sticking.
Can I replace the pressure control solenoid myself?
On some rear-drive transmissions it's reachable after dropping the pan and filter, so experienced DIYers can do it. You'll need the correct fluid, a torque wrench for the valve body bolts and a scan tool to reset adaptive values.