Chevrolet Transmission Pressure Control Solenoid Problem: Diagnostic Code P1860

You’re cruising down the road in your Chevy, and everything’s fine.  Then you notice it’s not.  It feels like it’s the transmission, and when it feels like a transmission problem, it usually is a transmission problem.

But that could be so many things and only an OBD-II Code P1860 can give you a clue as to what’s actually going on.

Fault code P1860, what is it?

Basically, a P1860 code tells you that there’s an issue with your torque converter clutch-pulse width modulation (TCC PWM) solenoid.  That’s a long name, but it’s really a simple concept.   A solenoid is, for all practical purposes, just a magnet; it’s a long, helical coil with positive and negative poles that create a magnetic field. 

The generated magnetism is what controls the hydraulic pressure that’s responsible for “translating” raw engine energy into motion.  The TCC PWM is typically found inside the body of the transmission, near the control valve, where it regulates the flow of fluid.  

It’s the transmission kingpin that lets automatic gears shift like they’re supposed to.  When there’s a problem related to the solenoid, whack, you’re in for some trouble.

What a P1860 Means For Your Chevrolet

Chevrolets aren’t the only vehicles that experience TCC PWM problems, but those issues do occur commonly among GM autos, particularly the older makes and models, such as the Silverado, Monte Carlo, Luminas, etc.  They also show up in older Buicks as well.

Trouble with a TCC PWM may start with some minor symptoms, but they’re guaranteed to get worse.  A few common problems include: 

• Slippage between gears, resulting in a jerking motion or sudden change in speed
• An activated “Check Engine” light
• Your engine stalls (a particularly dangerous thing at higher speeds or in heavy traffic)
• Lack of responsiveness to driver commands
• Reduced fuel efficiency
• Overheating (A really bad sign)

Driving your vehicle under these circumstances still may be possible, but it’s not advisable.  Aside from the traffic dangers they present, ignoring them may result in serious, or even irreparable, damage to your automatic transmission.  At the first sign of trouble, you need to pull over and get it checked. 

So:  What’s The Diagnosis?

Several things could be causing a P1860 code, and of course whatever the specific problem is determines the solution.  There are several possible scenarios:

Problem: Dirty or low transmission fluid.  A problem with your fluid can bring on just about any type of transmission diagnostic code, sending out sort of a general “distress signal” that something’s wrong.

Solution: If fluid is the problem, it’s the easiest and cheapest to fix (although shame on you for ignoring regular maintenance).  You need only to flush the system and fill with clean, high quality transmission fluid as soon as possible.

Problem: Broken or corroded wiring.  Bad wiring can cause a “misfire” in communication, triggering a P1860 code. Electrical components carry messages throughout your transmission system, so any disruption—such as a short-circuit, a damaged hiring harness, or faulty pin connectors--can distort those signals and result in an error code.  The same rings true for electrical problems with the TCM (Transmission Control Module), whose job is to also send commands to other parts of your transmission. 

Solution: Replace faulty wiring throughout the electrical parts of your transmission system, including all connectors and switches.

Problem: Your PCM (Powertrain Control Module) software needs updating.  The PCM is like a mini-brain that controls electrical messages throughout your transmission.  If your PCM is malfunctioning, it may need an upgrade.

Solution: Check with your auto’s manufacturer for any PCM-related recalls.  If one’s been issued for your vehicle, there may not be a charge to replace or upgrade it. 

Problem: A faulty solenoid. 

Solution: A replacement may be necessary.  In most cases, replacing it is a better option than trying to repair an older, damaged solenoid.  In some instances, replacing the valve may be all that’s needed, as valves can be damaged just through normal wear and tear. 

Preventing a P1860 Code

You can’t anticipate every potential auto problem!  The vehicle’s age, road history, weather, and a lot of other things just take their toll over time.  The best way to protect your transmission is through regular checks and maintenance, especially keeping the fluid full, clean, and flowing. 

And using only the best products and components will go a long way in staving off any problems.

Sun Transmissions can help you keep your vehicle in top operating shape.  We offer a comprehensive line of products for your automatic transmission, as well as for your power steering. 

From the smallest of parts—filters, gaskets, and switches—to overhaul kits and solenoids, we carry the best of what you need. We’d love to see you if you’re in the Miami area, but if not, we’ll be happy to ship to you.  Reach out to Sun Transmissions today!