1. Meaning of Code P138B
- Official Definition:
*”P138B – VCT System Oil Pressure Sensor – Circuit ‘A’ Range/Performance.”*
This code indicates an electrical or hydraulic anomaly in the oil pressure sensor circuit related to the VCT system, specifically on the “A” side of the engine (typically cylinders 1, 4, and 5 on V6/V8 engines). - Key Role:
The VCT system (“Variable Camshaft Timing“) adjusts camshaft timing in real-time to optimize:
▶️ Combustion,
▶️ Performance,
▶️ Fuel consumption.
2. Common Symptoms
- ✅ Check Engine Light (MIL) illuminated.
- ⚠️ Abnormal vibrations at idle (rough idle).
- 🔻 Noticeable power loss during acceleration.
- ⛽ Increased fuel consumption (+15-25%).
- ⚠️ Hard starting in cold weather.
- 🚫 Limp mode activation (limited power).
3. Probable Causes (by frequency)
| # | Cause | Technical Details |
|---|---|---|
| 1 | Inadequate engine oil | Incorrect viscosity (e.g., 5W-20 required but 10W-40 used), oxidized oil. |
| 2 | Hydraulic issue | Low level, clogged oil filter, worn oil pump. |
| 3 | Faulty pressure sensor | Internal failure, sensor clogged with deposits. |
| 4 | VCT solenoid failure | Circuit “A” stuck/open, burnt coil (resistance out of specification). |
| 5 | Wiring problem | Damaged wires, oxidized connectors, short circuit/poor ground. |
| 6 | Faulty PCM | Rare (diagnosed after eliminating other causes). |
4. Step-by-Step Diagnosis
Required tools: Advanced OBD-II scanner (e.g., FORScan), multimeter, oil pressure gauge.
| Step | Action |
|---|---|
| 1 | Check the oil : Level, viscosity, color. Change if necessary. |
| 2 | Test oil pressure (at idle/3,000 RPM): Normal value: 20-80 PSI. |
| 3 | Scan live data : – Compare oil pressure on side “A” with manufacturer specifications. – Observe VCT solenoid “A” status (% activation). |
| 4 | Inspect sensor/wiring : – Measure supply voltage (5V/12V). – Test continuity and resistance (typical value: 800-1200 Ω). |
| 5 | Check VCT solenoid “A” : – Expected resistance: 5-15 Ω. – Clean using specific degreaser. |
5. Repair Solutions
- Incorrect oil/low level :
→ Oil change + new filter + 5W-20/5W-30 synthetic oil (as per manual). - Faulty sensor :
→ Replace sensor on side “A” (cost: €70-160). - Faulty VCT solenoid :
→ Clean or replace (€120-220 part + labor). - Damaged wiring :
→ Repair wires/connectors (variable cost). - Low oil pressure :
→ Check oil pump/filter (total cost: €300-600).
Affected Ford models: F-150 (2015+), Explorer (2011-2020), Mustang (EcoBoost), Edge, Transit.
6. Average Repair Costs
| Intervention | Parts | Labor | Total |
|---|---|---|---|
| Sensor replacement | €70-160 | €50-90 | €120-250 |
| VCT solenoid replacement | €100-200 | €80-150 | €180-350 |
| Complete oil change | €40-70 | €30-60 | €70-130 |
7. Prevention Tips
- 🔧 Regular oil changes every 10,000-15,000 km (follow maintenance schedule).
- ⚠️ Use only recommended oil by Ford (avoid mixtures).
- 🔍 Monthly oil level check (cold engine, flat surface).
- 🧼 Clean VCT system every 60,000 km to prevent clogging.
Conclusion
Code P138B indicates a malfunction in the “A” circuit of the VCT system, often resolved by an oil change or replacing the pressure sensor/solenoid. Prompt action is crucial to prevent:
- Camshaft degradation,
- Chronic overconsumption,
- Turbocharger damage (on EcoBoost engines).
⚠️ Important : This code can be triggered by a simple drop in oil pressure. Consult a Ford specialist equipped with appropriate diagnostic tools (IDS/FDRS) for accurate troubleshooting.