P1870Manufacturer-specific code

P1870 Code: Transmission Component Slipping (GM)

On General Motors vehicles (Chevrolet, GMC, Buick, Cadillac), the P1870 code means a component in the automatic transmission is slipping. The check engine light comes on and you may feel vibration on the highway. On the 4L60E it is often a worn valve body.

Severity
High
Can I keep driving?
Yes, but with caution
Estimated cost
$150 to $2,500
Difficulty
Hard
System
Transmission
Applies to
Depends on the manufacturer

Common in: Chevrolet

Updated Reviewed by Renzo Chacca

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What the P1870 code means

P1870 is a manufacturer-specific code: the 1 in the second position means each automaker defines what it means, not the generic SAE standard. The most widespread definition is the one used by General Motors (Chevrolet, GMC, Buick, Cadillac). If your vehicle is another brand, confirm the code text with a scan tool that supports that manufacturer.

ManufacturerMeaning of P1870
General Motors (Chevrolet, GMC, Buick, Cadillac)Transmission component slipping

GM automatic transmissions (4L60E, 4L80E, 4T65E and others) use solenoids for shifting and for locking the converter, and they adapt clutch pressure with use.

The computer sets the P1870 code when converter slip is higher than normal with the clutch applied. On the 4L60E it is usually due to valve body wear.

Before you start repairs, confirm the make, model, year and engine. With manufacturer codes, the same number can change even between engines from the same brand.

P1870 code symptoms

  • Vibration or engine speed rising on the highway.
  • Check engine light on.

Likely causes of the P1870 code

  1. Worn valve in the valve body. The most frequent cause on the 4L60E.
  2. Converter solenoid. Confirm it with the tests in the diagnosis section.
  3. Low fluid. Check the level, condition and viscosity.
  4. Worn converter. Confirm it with the tests in the diagnosis section.

How to diagnose the P1870 code step by step

  1. Check the fluid.
  2. Watch the slip on the scan tool.
  3. Inspect the valve body.

How to fix the P1870 code

  • Repair the valve body with a kit.
  • Replace the solenoid or the converter.

Technical reference data

  • Slip with the converter locked: close to 0 rpm.
  • P1xxx codes are manufacturer-specific: confirm the definition with a scan tool that supports your brand.
  • Reference values: check the manufacturer data for your vehicle.

Brand-specific notes

On the 4L60E the valve body is a known wear point, so a valve body kit is often the right repair before anything bigger.

P1870 on GM

Very common on the Chevrolet Silverado, Tahoe, Suburban and GMC Sierra with the 4L60E transmission.

If your vehicle is another brand, check the table above for the meaning its manufacturer gives this code and confirm it with a compatible scan tool.

Frequently asked questions about P1870

What does the P1870 code mean on a GM?
It means a component in the automatic transmission is slipping. The check engine light comes on and you may feel vibration on the highway.
Does P1870 mean the same thing on every brand?
No. It is a manufacturer-specific code, so on other brands it may not exist or may mean something different. Confirm it with a scan tool that supports your make.
Can I drive with a P1870 code?
With caution. Severity is high with a P1870 code, because slipping wears the clutches quickly. Avoid heavy loads until it is checked.
How much does it cost to fix P1870?
Roughly $150 to $2,500 on a GM. A valve body repair is toward the lower end, while a converter or a rebuild costs the most.
Will a P1870 code clear itself?
Not while the slipping continues. Wear in the valve body or converter keeps bringing the code back.
What is the most common cause of P1870?
A worn valve in the valve body, especially on the 4L60E. The converter solenoid, low fluid and a worn converter come next.

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