Error Code P0201 is described as Cylinder 1 Injector Circuit Malfunction. This is set when the PCM (powertrain control module, also known as ECM or engine control module) determined a low or high voltage drop or resistance at the injector 1.

This code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II, or vehicles made in 1996 to present. Specifications in definition, troubleshooting and repairs vary from one make and/or model to another.

This code is very similar to P0200, P0202, P0203, P0204, P0205, P0206, P0207, and P0208. Additionally, this code can be seen in engine misfire, rich and lean conditions.

Definition

The PCM is equipped with special transistors called ‘drivers’ to operate the Fuel Injector On and Off in Fuel Injection System. The PCM then expects to see voltage close to battery voltage or “high”. If it doesn’t see the expected voltage, then it determines a problem, setting the Error Code P0201. Also, the PCM oversees the resistance in the circuit during normal operation, and if it sees the resistance is excessively low or high at cylinder 1 injector circuit, or out of its specifications, then it will set the same trouble code.

Common Symptoms

Error Code P0201 is quite unique, as symptoms can be felt even before the Check Engine light is activated in the dashboard. The vehicle may display rich or lean condition alongside with engine misfire. Other common symptoms include:

  • Poor acceleration and lack of power
  • Engine running rough
  • Engine dies or may not start at all
  • Excessive fuel consumption

Possible Causes

The most common causes for this code include:

  • Defective cylinder 1 injector
  • Plugged or dirt in fuel injector
  • Corroded fuel injector, connections or wiring
  • Poor electrical connections in the connector or harness
  • Open or short wiring harness
  • Damaged PCM

How to Check

As with most error codes, qualified mechanics check this error code by hooking it up to advanced scanner and check for the codes. Codes present will have their associated freeze frame data taken, which will tell the mechanic the conditions of the vehicle when the code was set, such as engine load, vehicle speed and operating temperature.

Then, the codes will be cleared and the vehicle will be taken for test drive to see if the problem comes back and registers to the scanner. If the code indeed comes back, the mechanic will proceed on conducting a visual inspection on the injector circuit and the fuel injector itself.

Then, the mechanic will test to injector for voltage to confirm proper operation. Using the scan tool, he will then monitor injector operation, along with a noid light (installed to the injector wiring) to test for the pulses of the fuel injector.

If these things check out, a manufacturer specific PCM test will be performed.

How to Fix

Repairs for this error code are pretty straightforward, which will be derived from a thorough diagnosis. Possible fixes include:

  • Replacement of the Cylinder 1 Fuel Injector
  • Repair or replacement of any wiring issues (damaged or broken wires)
  • Fixing poor connections
  • Replacement of the PCM

The problem for this code ranges from just annoying Check Engine light in the dashboard to various poor-running conditions. Nevertheless, any code that causes the vehicle’s engine to die while running should be fixed as soon as possible, as it can be dangerous for both the vehicle and the passengers of the vehicle.