P0261 Cylinder 1 injector circuit low

OBD-II Trouble Code - P0261 - Data Sheet

P0261 - Low signal in the cylinder 1 injector circuit.

This DTC indicates that transmission control module has detected a lower reference voltage coming from the number 1 cylinder fuel injector than specified by the vehicle manufacturer.

What does trouble code P0261 mean?

This Diagnostic Trouble Code (DTC) is a generic transmission code, which means it applies to OBD-II equipped vehicles. Although general, specific repair steps may differ depending on the brand / model.

OBD DTC P0261 is a generic transmission code common to all vehicles. Although the code is the same, the repair procedure may vary slightly depending on the manufacturer.

This code means that a low voltage condition has occurred in the powertrain control module (PCM) associated with the fuel injector for cylinder # 1 in ignition order.

In short, this fuel injector is malfunctioning for one of a variety of reasons. It is important to diagnose and fix this type of problem as soon as possible.

When the fuel injector is faulty, it will cause ripples on the line, which means engine operating parameters change due to mixed signals on the PCM.

Reducing the spray pattern of the fuel injector produces a lean mixture. Ripples begin. The oxygen sensor sends a lean signal to the PCM. In response, it enriches the fuel mixture flowing into all cylinders. Fuel consumption drops sharply.

A cylinder with a faulty injector creates a lean mixture, which in turn causes a higher temperature in the cylinder head, resulting in detonation. The knock sensor detects knock, signals the PCM, which reacts by slowing down the time. The engine now runs intermittently and lacks power.

The ripple effect does not end there, but it reflects the general idea.

Cross section of a typical automotive fuel injector (courtesy of WikipedianProlific):

Symptoms

Symptoms displayed for the P0261 code may include:

• The engine light will come on and a code P0261 will set.
• The engine will run more roughly than usual.
• Lack of power
• As a result, fuel economy will be significantly reduced.
• Uneven operation may occur engine on Idling
• Indecision or tripping while accelerating can happen
• Possibly available misfire in 1 cylinder

Causes of the P0261 code

Possible causes of this DTC:

• Dirty fuel injector feeding cylinder number one
• Defective fuel injector
• Clogged fuel injector
• Open or short circuit in the fuel injector harness
• Loose or corroded fuel injector connector
• The fuel injector on cylinder #1 may have a broken or weak internal return spring, which can result in a low reference voltage level.
• The wiring or connector associated with the number 1 cylinder can cause or cause connection problems, and connection problems can also result in low or inaccurate voltage levels.
• The powertrain control module may not function properly.

Diagnostics / Repair

Typically, this type of problem is associated with a loose or corroded electrical connector on an injector, a dirty injector (dirty or clogged), or a faulty injector that needs to be replaced.

For over 45 years, I have found that loose or corroded connectors have been the cause of electrical problems most of the time. I have only found a few instances where low voltage wiring shorted or opened (when not touched).

Most of the electrical problems were related to the alternator, starter solenoid wiring, oxygen sensor wiring due to close proximity to the exhaust system, and the battery. Most of the electrical work involved fixing customer-installed items such as high-power stereos and other parts or equipment that were incorrectly installed.

The fuel injectors are powered by the fuel pump relay. The PCM activates the relay when the key is turned on. This means that as long as the key is on, the injectors are powered.

The PCM activates the injector by supplying ground at the right time and for the right time.

• Check the connector on the fuel injector. It is a plastic connector attached to the injector with a wire clip around the connector. Pull on the connector to check if it detaches easily. Remove the wire clip and remove the connector from the injector.
• Inspect the harness connector for corrosion or extruded pins. Make sure the two blades are not bent in the injector itself. Repair any defect, apply dielectric grease and install the electrical connector.
• Start the engine and listen to the injector to make sure it works. Bring a long screwdriver to the injector and place the pen to your ear, and you can clearly hear the sound. If it does not emit a strongly audible click, then it is either not supplied with electricity, or it is faulty.
• If there is no click, remove the connector from the injector and check for the presence of power with a voltmeter. Lack of power means that the wiring to the fuel pump relay is faulty or poorly connected. If it has power, check both pins on the harness connector and if the PCM injector driver is working, the voltmeter will show fast pulses. If pulses are visible, replace the injector.
• If the nozzle worked, then it is clogged or dirty. Try to clear it first. The nozzle flush kit is inexpensive and will come in handy for the rest of the nozzles, possibly preventing repetition. If flushing does not solve the problem, the injector must be replaced.

Buy a “direct” nozzle flush kit online or at an auto parts store. It will consist of a high pressure injector cleaner bottle and a hose with an end to which the injector cleaner bottle can be screwed.

• Pull out the fuse to the fuel pump.
• Start the car and let it run until it dies due to lack of fuel.
• Remove and plug the fuel return line attached to the fuel pressure regulator. This is to prevent the vacuum cleaner from returning to the fuel tank.
• Remove the Schrader valve in the fuel rail inspection hole. Connect the flush kit fuel line to this test port. Thread the high pressure fuel injection cleaner bottle onto the flush kit fuel line.
• Start the engine and let it run until it runs out of fuel. It will only work on a bottle of cleaner.
• When the engine dies, turn off the key, remove the flush kit line and replace the Schrader valve. Install the fuel pump fuse.

How does a mechanic diagnose a P0261 code?

• A mechanic can diagnose this DTC by looking at the cylinder number 1 fuel injector.
• Once the fuel injector on cylinder number 1 is located, the mechanic should check the fuel injector using the manufacturer's suggested procedure. This test will show if the internal spring has failed due to the reference voltage generated by the fuel injector during this test.
• The mechanic will then check the wiring and connector associated with the fuel injector on the number 1 cylinder for damage.

If the problem is still not found after performing these tests, the powertrain control module may be faulty and should be checked by a mechanic. Once the mechanic has made a decision, he/she will share this information with the client.

Common Mistakes When Diagnosing Code P0261

A common mistake would be to replace the fuel injector in cylinder #1 without checking its circuitry for damage. Although a bad injector is the most common cause of this DTC, it is not the only cause, so it must be proven that all other possible causes of this problem are not the cause.

How serious is the P0261 code?

Any DTC associated with a bad fuel injector is a serious problem. This can affect the performance of your engine and, if left aside, can result in engine damage. It is best to diagnose and fix this problem as soon as possible to keep your car's engine in good working order.

What repairs can fix code P0261?

• Replacing the fuel injector on 1 cylinder
• Repair or replace wiring or connectors that are connected to the fuel injector on cylinder #1
• Powertrain Control Module Replacement

Additional comments regarding code P0261

Regular maintenance of the fuel system, such as fuel system cleaning may help prevent this DTC from occurring. These cleaners will pass through the fuel injectors, providing the lubrication needed for small internal parts to prevent potential breakage of the return springs inside the fuel injector. This service should be performed at least once a year, but for best results, perform it at every oil change.

Harley DTCs P0261 P0263 P1003

Need more help with your p0261 code?

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