B1303 Mazda CU-X Diagnostic Trouble Code

B1303 Mazda CU-X code definition:
B1303 is a kind of OBD-II Diagnostic B-Body Diagnostic Trouble Code for Mazda CU-X.

B1303 Mazda CU-X shows up when there's an electrical problem that causes the fuel volume regulator to malfunction and open. It's quite an unusual problem and likely intermittent. If the car doesn't start, they will proceed by testing the voltage at the fuel pump connector and see if the fuel pump relay, fuse, and PCM circuitry should be inspected.

Symptoms

Symptoms of a B1303 Mazda CU-X diagnostic trouble code may include:
  • If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected
  • Corroded or damaged connector
  • Reduction in engine performance, especially at low RPM levels
  • Hesitation upon acceleration
Place of B1303 in engine

Possible Causes :

  • A plugged converter will cause of host of driveability problems as well as set this code. A severely plugged converter will result in the inability to increase rpm when under load. Look for a code such as P0421 -- catalytic converter efficiency below threshold if the converter indicating a faulty converter.
  • Dirty air cleaner element Damaged DPF
  • Fuel with a large percentage of sulfur will clog the DPF quickly

Common Misdiagnoses

  1. Crankshaft Position Sensor Circuit Performance Problem
  2. TP Sensor Learn Not Complete Problem
  3. Low Coolant Circuit Problem
  4. Cruise Control System - Vehicle Accel Too High Problem
  5. Kick-Down Switch Failed Short 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. 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. Look for damage to the tank indicating impact that may have damaged the fuel pump or sender.

Process Tips

Diagnostic trouble code B1303 Mazda CU-X 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 B1303 Mazda CU-X.

Fortunately, B1303 Mazda CU-X is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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