What does it mean?
This is a generic powertrain diagnostic trouble code (DTC) and generally applies to OBD-II equipped vehicles with cruise control. Vehicle makes may include, but are not limited to, Chevrolet (Chevy), Toyota, Ford, Harley, Dodge, Ram, Ford, etc.
The ECM (Engine Control Module) spends most of its time ensuring your engine runs as it should while keeping the manufacturer’s emissions, fuel economy, performance, noise, and comfort functions at acceptable levels. Cruise control is a great feature for long trips since you don’t need to control the vehicle’s speed. The ECM can handle it as long as the cruise control is free from any faults. If you’re reading this, your cruise control has likely stopped working. A good sign that the cruise control has been completely disabled by the ECM is that the cruise control indicator light on the dashboard does not illuminate when you try to activate it.
Generally, this fault code means that the command input has experienced an electrical malfunction originating from many potential causes. The P0577 Cruise Control Input Circuit High and related codes (P0575 and P0576) are set when the ECM detects a malfunction in the cruise control input circuit, in this case, it means there is a high voltage condition.
Cruise Control Switches:
P0577 Brake Switch
How severe is this DTC?
This particular code is actually a mild issue that does not require immediate repair as the engine’s performance will not suffer, allowing the vehicle itself to be operational. Not being able to use cruise control is the only major problem with this type of code.
That said, it is important to note that when the ECM displays a P0577, or any other P code for that matter, the vehicle may not be able to pass an emissions test. This is why clearing the code after each repair is essential before performing a new test. The mechanic will not be able to identify the exact problem if it is ignored, and it could lead to more serious issues in the future.
What are some of the symptoms of the code?
The most common symptom regarding the P0577 code is the fact that the cruise control system itself or one of its functions stops working. Other potential symptoms may include:
CEL (Check Engine Light) will illuminate after a few driving cycles once the ECM has detected a problem
Irregular or intermittent operation of cruise control functions
The cruise control indicator light is permanently on or does not illuminate
What are some of the common causes of the code?
Causes
of this P0577 cruise control code can include:
The most common cause of abnormal voltage/resistance level in the cruise control input circuit is a faulty cruise control switch, which could be caused by spilled liquids short-circuiting the device and/or the circuits inside.
Wiring problem (e.g., open circuit, short to ground, short to power, etc.)
ECM (Engine Control Module) problem (i.e., internal short, open, etc.)
Open or shorted cruise control switch(es)
Damaged connectors in the cruise control system
Blown fuses, which could indicate a much more serious problem. (e.g., short circuit, voltage spikes, faulty control module(s), etc.)
What are the diagnostic and troubleshooting steps for P0577?
The first step in the troubleshooting process for any malfunction is to search the Technical Service Bulletins (TSBs) for known issues with the specific vehicle.
Advanced diagnostic steps become very vehicle-specific and may require the appropriate advanced equipment and knowledge to operate accurately. We include the basic steps below, but refer to a repair guide specific to the year/make/model/powertrain for steps specific to your vehicle.
Basic Step #1
After recording the active P0577 code with your OBD-II DTC scanner, you should perform a thorough inspection of the connectors, wiring, and other parts of the vehicle’s cruise control. It is also important that any damaged connectors (e.g., broken tabs, heat damage, corroded, etc.) are replaced, reconnected, or repaired as necessary. You will need to clear the code and perform a test drive, try using the cruise control functions now. If everything works after the repair, you must ensure that the CEL (Check Engine Light) does not come back on. Otherwise, if it illuminates again and the code has been recorded in the ECM again, continue your diagnostics.
Basic Step #2
Test the cruise control switch (AKA: multifunction switch). Refer to your brand and model’s service manual for the desired values and diagnostic procedures specific to your vehicle. Most of the time, this will involve using your DVOM (or multimeter) to record the present electrical values. After comparing your actual values to those desired by the manufacturer, you will be able to identify the switch as the problem or rule it out as a possibility.
Basic Step #3
If the switch has been confirmed as faulty, replacing it may not be an easy task, given that there may be airbags in the way of replacement. That said, it could be as simple as removing 1 or 2 steering column covers to access the switch. If you have identified it as your problem, found it faulty, and replaced it following the steps specific to your vehicle, test the vehicle after clearing the active codes.
This article is strictly for informational purposes only, and the technical data and service bulletins for your specific vehicle should always take precedence.