C0638 Engine Trouble Code
What is C0638?
C0638 indicates potential catalytic converter failure. If completely failed, your vehicle may not run properly and fuel economy will suffer significantly. Average replacement cost is $2,000–$2,140. This repair requires professional service and should not be delayed.
Code Information
| Code Type: | OBD-II Chassis (C) Trouble Code |
| System: | Chassis |
| Code: | C0638 |
C0638 Symptoms
Check Engine Light
Illuminated dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration
Starting Problems
Difficulty starting the engine
C0638 Code Structure
Understanding what each digit means in the C0638 chassis trouble code:
| C | 0 | 6 | 3 | 8 |
|---|---|---|---|---|
| Chassis Code | Intake Valve Control Solenoid Circuit Low | Fuel Temperature Sensor B Circuit Range/Performance | Injection Pump Fuel Metering Control 'A' High | Clutch Position Sensor Circuit Malfunction |
How to Fix C0638
Diagnostic Steps:
The catalytic converter has oxygen sensors before and after it. When warm and in closed-loop mode, the upstream O2 sensor reading should fluctuate, while downstream should remain steady.
Repair Solution:
Power steering pressure switch monitors system operation. If pressure changes are not detected after calibrated speed transitions, this DTC sets. Verify PSP switch operation and check for circuit opens or shorts.
Technical Notes:
C0638 DTCs can be triggered by upstream issues. For example, a dirty MAF sensor may cause incorrect fuel-trim adjustments, leading oxygen sensors to report mixture problems. Address root causes first.
C0638 Description
C0638 engine trouble code is related to Clutch Position Sensor Circuit Malfunction.
Main Cause
The primary reason for C0638 OBD-II Engine Trouble Code is: Fuel Temperature Sensor B Circuit Range/Performance.