U140B Oldsmobile Custom Diagnostic Trouble Code

U140B Oldsmobile Custom code definition:
U140B is a kind of OBD-II Diagnostic U-Network Diagnostic Trouble Code for Oldsmobile Custom.

U140B Oldsmobile Custom is defined as Camshaft Position Sensor A Circuit Low. This means the CMP (camshaft position) sensor circuit on engine bank 1 sends an irregular reading. There are two wires dedicated for each coil; one is battery feed which usually comes from the distribution center, and the other one for the coil driver circuit from the PCM. The PCM grounds or ungrounds the circuit to activate or deactivate the coil.

Symptoms

Symptoms of a U140B Oldsmobile Custom diagnostic trouble code may include:
  • Hesitation upon acceleration
  • Excessive exhaust leak
  • Rich or lean exhaust
  • Lack of power
Place of U140B in engine

Possible Causes :

  • Faulty IMRC actuator relay (if equipped)
  • A large air leak at or near the number one oxygen sensor would also cause a lean mixture.
  • Some aftermarket accessories and performance modifications

Common Misdiagnoses

  1. IC Circuit High Voltage Problem
  2. Control Module Throttle Actuator Position Performance Problem
  3. Air Conditioning (A/C) Clutch Feedback Circuit High Voltage Problem
  4. Cruise Vehicle Speed/Set Speed Difference Too High Problem
  5. PCM Stack Overrun Problem

Repair Processes :

Use the DVOM to test resistance and continuity on all system circuits if actuator and sensor resistance levels are in compliance with manufacturer's specifications. With the valve disconnected, the red voltmeter lead should be attached to the IMRC valve power wire and the black voltmeter lead connected to ground. If the engine displays a miss and there wasn't a code, determine which cylinder is misfiring. If the exhaust manifold is visible, spay or pour a small amount of water on each cylinder exhaust port. Water will evaporate immediately on good cylinders and slowly on the missing cylinder. If this can't be accomplished pull the plugs and check the condition.

Process Tips

Diagnostic trouble code U140B Oldsmobile Custom is not difficult to diagnose and repair. Thus, it always pays to have a qualified technician to look after your vehicle should this error code arise.

Diagnosing this code requires the engine to be in good running shape, without unmetered air entering the engine. If other codes that relates to misfiring condition, lean running or air entering the engine is present, then you must first fix those error codes before U140B Oldsmobile Custom.

Fortunately, U140B Oldsmobile Custom is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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