P1390 VCT Solenoid B Malfunction
The P1390 code indicates a malfunction in the Variable Cam Timing (VCT) solenoid B, which controls oil flow to the cam phaser on bank 2 (typically the rear bank on V6/V8 engines). The PCM detects that the solenoid's electrical response or mechanical operation does not match expected parameters, often due to electrical faults, oil contamination, or mechanical binding.
01. Most Common Causes
- Faulty or stuck VCT solenoid B due to oil sludge or debris
- Short to ground, short to voltage, or open circuit in solenoid B wiring
- Corroded, loose, or moisture-damaged solenoid connector
- Worn or seized cam phaser (VCT actuator)
- Low engine oil pressure or incorrect oil viscosity
- Clogged solenoid oil screen or filter
- Intermittent PCM failure (less common)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Rough idle or engine hesitation
- Reduced fuel economy and performance
- Possible engine knock or rattling from timing chain area
03. Step-by-Step Diagnosis
Scan for additional codes and freeze frame data
Inspect VCT solenoid B connector for corrosion, damage, or loose pins
Test solenoid resistance and power/ground circuits with a multimeter
Check engine oil level, condition, and pressure
Remove and inspect solenoid for sludge or debris; clean or replace as needed
Perform a cam timing correlation test with a scan tool to verify phaser operation
1. Frequently Asked Questions
Is it safe to drive?▼
You can drive short distances, but continued operation may cause reduced performance, increased emissions, and potential engine damage if the cam timing is severely off. Have it diagnosed promptly.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400 for solenoid replacement, plus diagnostic fees. If the cam phaser or wiring is involved, costs can exceed $800.