P0803 OBD-II Trouble Code: Upshift Solenoid Control Circuit Malfunction

P0803 code definition

The P0803 code is known as the 1-4 Upshift (Skip Shift) Solenoid Control Circuit Malfunction.

What the P0803 code means

The P0803 fault code is only found in manual vehicles, because it’s part of the system that prevents the driver from intentionally shifting past second and third gears. The skip shift solenoid control circuit is put in place to enhance fuel economy and protect the engine by eliminating the high RPMs required to shift from first gear to fourth, bypassing second and third. This code is set if the PCM (powertrain control module) detects voltage or resistance outside the norm from the skip shift control circuit.

What causes the P0803 code?

The skip shift control circuit is fairly simple, so there is a limited number of issues that cause this fault code to occur. These include: * A defective skip shift solenoid * A defective skip shift relay, fuse, or actuator * Connector or wiring damage or short * Installation of an aftermarket skip shift bypass (disables the upshift solenoid control circuit, allowing the driver to shift from first to fourth gear)

What are the symptoms of the P0803 code?

The most common symptom of a skip shift control circuit malfunction is an illuminated Check Engine or Service Engine Soon light. The intended function of the solenoid may be disabled.

How does a mechanic diagnose the P0803 code?

The root cause of this code may be diagnosed via the following steps:

• Use of an OBD-II scanner in order to record stored codes and freeze frame data
• Use of a scan tool to attempt to turn the solenoid on and off
• Measuring the current of the upshift solenoid control circuit at the PCM connector to ensure that it draws the appropriate value
• Visual inspection of connections and wiring to the solenoid

Common mistakes when diagnosing the P0803 code

A faulty skip shift solenoid control circuit can be difficult to diagnose because in some instances, the vehicle won’t store the code until the fault occurs multiple times. In addition, the Check Engine light is not always triggered by the solenoid’s failure.

How serious is the P0803 code?

The P0803 code is not particularly worrisome. The vehicle will still function, although it may no longer prevent you from shifting up and bypassing the lower gears. This failure can, however, cause reduced fuel efficiency and possible emissions problems.

What repairs can fix the P0803 code?

Your technician will follow a series of procedures in order to repair this faulty system. Depending upon the component that is defective, one or more of the following may be performed:

• Wiring replacement
• Solenoid actuator or relay replacement
• Replacement of the solenoid connector at the PCM (powertrain control module)
• Skip shift solenoid replacement
• Clearing of trouble codes in the vehicle’s computer and retesting to be sure that the problem has been resolved

Additional comments for consideration regarding the P0803 code

Although a faulty upshift solenoid control circuit is not a major issue in your vehicle’s operation, it still may cause you some grief. Certain states may not pass your vehicle in their emissions testing if it is setting this fault code. In addition, because the system is often designed so that it doesn’t set a code or trigger the Check Engine light until the problem recurs multiple times, you may experience a loss in fuel economy before you realize there’s an issue. Installing an aftermarket skip shift solenoid bypass can also cause problems if you don’t know that your vehicle is throwing a code. If this bypass resistor burns out, the vehicle will likely perceive the event as a skip shift solenoid fault, resulting in the same stored code, potentially without your knowledge.

Need help with a P0803 code?

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