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Error Code P0577 is defined as Cruise Control Input Circuit High. This code is a generic trouble code that applies to vehicles equipped with OBD-II and with cruise control. It is particularly common, but not limited to Chevrolet (Chevy), Dodge, Ford, Harley, and Ram. Specifications on the definition, troubleshooting, and repairs, of course, vary from one powertrain type, make and model to another.
The PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) spends most of its time making sure the engine is running properly. It tries to keep performance, fuel economy, emissions, noises, creator comfort functions, etc., at an acceptable level. Cruise control is one important feature especially for long trips, as it provides drivers the help they need in controlling the speed of the vehicle. The PCM can take care of this function, as long as the cruise control system is free of any problems. When the cruise control light is activated on the dash that means the PCM has disabled the cruise control system.
Error Code P0577 means Cruise Control Input Circuit High.
Other related error codes include:
Aside from the activation of Check Engine light, Cruise Control light, stored code, the most common symptom for this trouble code is non-functioning cruise control system. Other symptoms include erratic or intermittent cruise control function(s).
The most common cause of this code is abnormal voltage/resistance level in the cruise control input circuit, which is a result of faulty cruise control switch due to shorted circuitry from leaking or spilled liquids.
Other possible causes include:
- Shorted or open wiring
- Damaged connectors within the cruise control system
- Open or shorted cruise control functions switch harness
In some cases, a blown fuse can cause this code, which could be a symptom of a more significant problem.
How to Check
As with most codes, it is best to check with the TSB (Technical Service Bulletin) for known issues, troubleshooting, and repairs for the error code.
Advanced diagnostic steps are usually vehicle specific, and may require sophisticated equipment and tools to perform accurately.
Record the active code with your OBD-II scanner, then inspect the vehicle’s connectors, wirings, and other components of the cruise control system. Look for any damaged parts, especially connectors (i.e., heat tabs, broken tabs, corroded connectors, etc.). Repair or replace when necessary.
Make sure you clear the codes and perform a test drive, try using the cruise control functions this time.
If it’s working after repair, then make sure the Check Engine light is no longer active on the dashboard. If it lights up again, then that means the code has been stored in the PCM again. Thus, continue the diagnosis.
Test the switch control switch (malfunction switch). Refer to your service manual for the specific repair and get the right desired values and diagnostic procedure. Use DVOM (or multimeter) to record the electrical values present. Compare the actual values to the specifications set by the manufacturer. This will help you pinpoint if the switch is the issue, or rule it out as a possibility.
A defective switch must be replaced. This can be quite a difficult task, since there are other things in the way, such as the airbags. With that said, it could also be as simple as removing 1 or 2 steering column covers to get access to the switch.
If you have determined it as defective, then replace following the specific steps set by the manufacturer for the vehicle. Take the vehicle for a test drive and clear the active codes.
How to Fix
Common repairs for this code include:
- Replacement of damaged cruise control switch
- Repair of any fluid or leaks that caused the malfunction
- Repair or replacement of shorted or open wiring
- Repair or replacement of open or shorted cruise control function switch harness
- Replacement of damaged connectors in the cruise control system
- Replacement of blown fuses (if this is the issue, then it’s important to have the mechanic check the vehicle thoroughly for more problems)
This code is a minor issue that doesn’t require immediate repair. The vehicle is still operational, and engine performance won’t suffer.
The most common mistake in addressing this issue is unnecessarily replacing components when the problem was actually a blown fuse. Thus, it’s important to check for blown fuses before replacing any components and then conduct a retest to see if the fuse was actually causing the issue.