Common Causes for P0585 code
From what I’ve seen in the shop, there are a handful of usual suspects when it comes to the P0585 code. Most often the issue is with the multi-function switch itself-it can wear out or develop internal faults. Other times, the wiring or connectors for the cruise control system get damaged, corroded, or shorted. I’ve also run into cases where the cruise control servo motor goes bad, or there’s a problem with the PCM or its programming. Here’s a quick rundown of the most common causes I encounter:
- Faulty multi-function switch (the stalk on your steering column)
- Bad cruise control servo motor
- Broken, shorted, or corroded wiring/connectors in the cruise control circuit
- Faulty cruise control module or PCM (sometimes a software glitch)
In rare cases, it can be a combination of these, so it’s important to check everything step by step.
Symptoms of obd2 code P0585
When this code is active, you’ll usually notice your cruise control just won’t work at all. Sometimes, the cruise control light on your dash might flash, not come on, or not respond when you try to set your speed. I’ve also seen cases where the speedometer or odometer acts jumpy or unreliable, but that’s less common. If you see other warning lights or codes, they might be related, especially if they mention the throttle or speed sensors.
Diagnosis Steps for dtc P0585
Here’s how I personally go about diagnosing a dtc P0585. First, I always start with the basics-give the wiring and connectors for the cruise control system a good visual inspection. Look for anything loose, corroded, or damaged. Don’t forget to check the connectors at the multi-function switch and the cruise control servo. Next, I hook up a scan tool to pull all stored codes and freeze-frame data. It’s smart to write this info down, since it can help you spot patterns or related issues. Clear the codes and take the car for a test drive to see if the code comes back. If it does, it’s time to get out the digital volt/ohm meter (DVOM). I check for proper voltage and ground at the multi-function switch. If there’s no power or ground, I check the fuses-make sure to test them with the circuit loaded, not just visually. If power and ground are good, I disconnect the switch and test it according to the manufacturer’s specs. If the switch fails, that’s your culprit. If it checks out, I move on to testing the cruise control servo motor the same way. If both the switch and servo are good, I check the wiring between them for continuity and resistance, making sure there are no breaks or shorts. Sometimes, the problem can be in the PCM or the cruise control module, especially if everything else checks out. In those cases, I look for any technical service bulletins (TSBs) that might point to a known issue or software update. It’s best to have someone assist you when checking the switch and servo, since some tests require the switch to be operated while you measure.
Common Mistakes When Addressing P0585 engine code
One thing I see a lot is people jumping straight to replacing the multi-function switch without checking the wiring or connectors first. That’s a surefire way to waste money and time. Another common mistake is skipping the fuse check or not testing them under load-sometimes a fuse looks fine but fails when current actually flows. I also caution against ignoring related codes, especially those for the throttle position sensor or speed sensors. They can be tied to the same circuit and cause similar issues. Don’t just clear the code and hope for the best-track down the root cause before swapping any parts.
Seriousness of P0585 Issues
While this code isn’t as severe as some others, it’s not something to ignore if you rely on cruise control. The main risk is losing cruise control functionality, which can be inconvenient and, in some cases, distracting if you’re used to using it on long drives. If the wiring issue is severe, it could potentially affect other systems that share the multi-function switch, like turn signals or wipers. In rare cases, ignoring electrical faults can lead to further damage to the PCM or related modules. Honestly, it’s best not to put this off for later-things can go south quickly if a wiring problem spreads.
Repair Guide for P0585 trouble code
Here’s what I usually do to fix a P0585 trouble code, based on what the diagnostics show:
- Replace the multi-function switch if it fails testing
- Repair or replace any damaged wiring or connectors in the cruise control circuit
- Replace the cruise control servo motor if it’s faulty
- Update or reprogram the PCM if there’s a known software issue (per TSBs)
- Replace the PCM or cruise control module only as a last resort, after all other checks
Conclusion
To sum it up, code P0585 means your cruise control system isn’t getting the right signals from the multi-function switch, usually due to a faulty switch, wiring issue, or sometimes a bad servo or module. It’s not the most dangerous code out there, but you shouldn’t ignore it-especially if you use cruise control often. Start with simple checks like wiring and fuses, then move on to testing the switch and servo. Most of the time, fixing or replacing the faulty component will get you back on the road with a working cruise control. Don’t put off the diagnosis, and always make sure the root cause is fixed before clearing the code. That’s the most reliable way to keep your car safe and trouble-free.
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