P1550 is a manufacturer-specific powertrain code. Its exact definition depends entirely on the vehicle application, ranging from a power steering pressure sensor fault to a barometric pressure sensor issue.
Because definitions vary widely, the exact application must be verified before diagnosis. The code identifies a detected condition and does not automatically confirm a single failed component.
Quick Navigation
Key Takeaways
- P1550 is a manufacturer-specific code with definitions varying by vehicle make and model.
- On some Ford and GM applications, it indicates a power steering pressure sensor circuit malfunction.
- On certain Toyota and Lexus applications, it points to a barometric pressure sensor circuit fault.
- Diagnosis requires confirming the exact factory definition and testing the specific monitored circuit.
P1550 Code Description and Implications
P1550 is a manufacturer-specific code, meaning its exact definition depends on the vehicle application.
Some Ford and GM applications: P1550 indicates a malfunction in the power steering pressure (PSP) sensor circuit. The PCM monitors this sensor to adjust idle speed when steering load increases.
Certain Toyota and Lexus applications: P1550 indicates a fault in the barometric pressure (BARO) sensor circuit, which the ECM uses to adjust fuel delivery based on atmospheric altitude and pressure.
Other verified applications: The code may relate to cruise control servo circuits, idle speed control actuators, or electronic throttle control systems.
When diagnosing an OBD2 problem, verifying the exact factory service information for your specific vehicle is critical.
Common Causes of the P1550 Code
The underlying causes depend entirely on which system the code monitors on your specific vehicle.
Power Steering Pressure Sensor Applications: A failed PSP switch or sensor, low power steering fluid, a failing power steering pump, or damaged wiring in the sensor circuit.
Barometric Pressure Sensor Applications: A failed BARO sensor, an open or short in the sensor reference, signal, or ground circuits, or a failed ECM.
Cruise or Idle Control Applications: Faulty cruise control servos, idle air control valves, or damaged mechanical linkages and wiring harnesses.
Symptoms Associated With P1550
Symptoms vary significantly based on the affected system and the vehicle application.
On power steering applications, you may notice erratic idle speeds when turning the steering wheel, or the power steering system may feel unusually heavy.
On barometric pressure applications, the engine may run poorly, hesitate during acceleration, or exhibit poor fuel economy due to incorrect altitude compensation.
On cruise or idle control applications, the cruise control may become inoperative, or the engine may stall or idle roughly when coming to a stop.
The Check Engine Light will illuminate, and MIL behavior varies by application.
Diagnosing the P1550 Trouble Code
Diagnosis must begin by confirming the exact factory definition for your specific make, model, and engine.
For power steering applications, check the power steering fluid level and inspect the pump and hoses for leaks. Test the PSP sensor signal voltage while turning the steering wheel.
For barometric pressure applications, compare the scan tool BARO reading with a known-good absolute pressure reference, and test the sensor reference, signal, and ground circuits.
For cruise or idle systems, inspect the respective actuators, linkages, and wiring for physical binding or electrical faults.
Repairing the P1550 Issue
Repairs must follow confirmed diagnosis based on the specific monitored system.
If the PSP sensor is confirmed faulty, replace the sensor and top off the power steering fluid with the correct specification.
If the BARO sensor fails testing, replace the sensor and clear the adaptive memory if required by the manufacturer.
If wiring damage is found in any of these circuits, repair the harness and secure it away from heat and moving components.
Cost Considerations for P1550 Repairs
Repair costs vary considerably depending on the confirmed root cause and the specific vehicle application.
Replacing a power steering pressure sensor or barometric pressure sensor involves standard parts costs and minimal labor.
Repairing a power steering pump or cruise control servo involves higher parts and labor costs.
Cost depends on diagnostic time, component accessibility, required parts, programming requirements, and labor.
Prevention Strategies for Future Occurrences
Preventing these faults requires maintaining the specific systems monitored by the code.
For power steering applications, maintaining proper fluid levels and addressing leaks promptly helps prevent sensor and pump damage.
Inspecting exposed engine bay wiring and sensor connectors can help identify developing chafing or moisture intrusion before it causes an electrical fault.
Troubleshooting Tips and Best Practices
Always check for Technical Service Bulletins related to P1550 for your specific vehicle application.
Manufacturers may release updated sensor part numbers, revised wiring harness pigtails, or software updates for the control module.
Do not assume a specific sensor requires replacement simply because its name appears in a generic code description.
Verify the exact factory wiring diagram and pinout before performing electrical tests to avoid misdiagnosing a shared circuit.
More OBD-II Codes
| P1546 | P1542 | P1531 | P1529 |
| P1525 | P1524 | P1555 | P1565 |
| P1571 | P1574 | P1580 | P1586 |
| P0551 | P0107 | P0108 | P0571 |
| P0573 | P0505 | P0506 | P1519 |
| P1520 | P1587 | P1588 | P1500 |
Frequently Asked Questions
Is the P1550 code generic or manufacturer-specific?
No. P1550 is a manufacturer-specific code. Its exact definition depends entirely on the vehicle application, such as a power steering or barometric pressure sensor fault.
Can low power steering fluid cause a P1550 code?
On applications where P1550 monitors the power steering pressure sensor, low fluid can cause erratic pressure readings, potentially triggering the code.
Will disconnecting the battery clear the P1550 code?
Disconnecting the battery may temporarily clear the code, but it does not repair the underlying electrical or mechanical fault. It also erases valuable freeze frame data.
Can I drive my vehicle with a P1550 code?
Driving depends on the affected system. A barometric sensor fault may cause poor drivability, while a power steering sensor fault may cause erratic idle or heavy steering.
Does P1550 mean the PCM must be replaced?
Not necessarily. While a PCM failure is possible, a failed sensor, an open wire, or a mechanical issue in the monitored system are much more common causes.
What Should You Do About the P1550 Code?
Confirm the exact factory definition and diagnostic procedure for your specific vehicle application before attempting repairs.
Do not assume a specific sensor requires replacement based solely on the presence of the diagnostic trouble code.
Inspect the relevant system components, verify connector integrity, and test the applicable circuits to rule out external faults.
Follow the applicable manufacturer diagnostic workflow to isolate the relevant system and components before replacing any hardware.
