C1940 Engine Trouble Code
What is C1940?
C1940 code can indicate a faulty oxygen sensor, which may eventually damage the catalytic converter (repair cost: $2,000–$2,200). Professional diagnosis costs around $200–$210. Oxygen sensors are often straightforward to replace — check your owner's manual for location and instructions. This issue should be addressed promptly to prevent further damage.
Code Information
| Code Type: | OBD-II Chassis (C) Trouble Code |
| System: | Chassis |
| Code: | C1940 |
C1940 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
C1940 Code Structure
Understanding what each digit means in the C1940 chassis trouble code:
| C | 1 | 9 | 4 | 0 |
|---|---|---|---|---|
| Chassis Code | Fuel And Air Metering | Injector Circuit Malfunction - Cylinders | Injection Pump Fuel Metering Control 'B' High | Shift Solenoid E Performance or Stuck Off |
How to Fix C1940
Diagnostic Steps:
Regarding C1940, carefully inspect the wire harness near the intake manifold bracket, best accessed from below near the oil filter. Look for chafing, pinching, or damaged insulation.
Repair Solution:
Excessive air inflow may result from vacuum leaks, dirty sensors, or EGR valves not closing properly. Insufficient fuel can stem from dirty injectors, clogged filters, weak fuel pump, or leaking pressure regulator.
Technical Notes:
C1940 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.
C1940 Description
C1940 engine trouble code is related to Shift Solenoid E Performance or Stuck Off.
Main Cause
The primary reason for C1940 OBD-II Engine Trouble Code is: Injector Circuit Malfunction - Cylinders.