P0894 – Transmission component slipping

Reinier

By Reinier (Contact Me)
Last Updated 2017-07-12
Automobile Repair Shop Owner

Trouble CodeFault LocationProbable Cause
P0894 Transmission component slipping Mechanical fault

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What Does Code P0894 Mean?

OBD II trouble code P0894 is a generic code that is defined as “Transmission component slipping”, and is set when the PCM (Powertrain Control Module) detects that the rotational speed of one or more rotating components of the transmission is lower than expected.

While the setting parameters of this code vary greatly between applications, all applications use input data from the throttle position sensor, engine speed sensor, vehicle speed sensor, and others to monitor and control the functioning of the automatic transmission. Based on the input data from various engine and transmission sensors, the PCM expects to see various parts of the transmission rotate at speeds that agree with pre-programmed values.

In practice, this means that if the engine is rotating at a given speed, the torque converter should rotate at the same speed. More importantly though, and depending on the currently selected gear, the transmission output shaft should rotate at a speed that corresponds to a pre-programmed value that takes into account the gear ratio reduction that applies to the selected gear, regardless of the engine speed while that gear is selected.

The above is saying a lot, but all it means is that if the engine is rotating at say, 3 000 RPM, all parts of the transmission should rotate at a speed that corresponds to that engine speed, given the currently selected gear. Thus, if the output shaft speed is lower than expected, the PCM will deduce that a transmission component is slipping relative to one or more other components, and it will set code P0894 as a result.

The image below shows the maze of fluid passages in a relatively uncomplicated automatic transmission valve body. Note that even a partial blockage of any of the passages can cause a valve shuttle or ball check valve not to move freely, which is often a cause of code P0894.

Valve body

What are the common causes of code P0894 ?

Some common causes of code P0894 could include the following-

  • Low transmission fluid levels
  • Dirty, contaminated, or degraded transmission fluid
  • The use of unsuitable transmission fluid that can affect lubrication and/or power transfer
  • Blockages in the valve body that prevent valve shuttles from moving freely
  • Defective shift solenoids
  • Internal transmission wiring failures
  • Mechanical failure of one or more transmission components

What are the symptoms of code P0894 ?

Common symptoms of code P0894 could include the following-

  • Stored trouble code, and possibly an illuminated warning light
  • Gear shifts may be harsh, erratic, or unpredictable
  • The transmission may not shift between certain gears
  • In some cases, the transmission may not shift at all
  • Transmission may hesitate before shifting into gear, or may not engage any gear
  • Transmission may overheat
  • Depending on the nature of the problem, the transmission may be noisy, or emit whining, rumbling, or even knocking sounds
  • In some cases, fuel consumption may increase considerably
  • In most instances of code P0894, other transmission related code may be present as well

How do you troubleshoot code P0894 ?

NOTE #1: Diagnosing this code requires a dedicated transmission fluid pressure gauge. Most transmissions have several pressure testing points, and the pressure being delivered to these ALL points must be checked in order to make an accurate diagnosis.

NOTE #2: Transmissions that have “life-time” fills can generally not be repaired on a DIY basis, since draining and refilling these transmissions almost always requires special equipment and tools that are not available to the average non-professional mechanic.  If the affected application has a “life-time” transmission fluid fill, the better option is to refer the vehicle to the dealer or other competent repair facility for professional diagnosis and repair.

Step 1

Record all fault codes present, as well as all available freeze frame data. This information can be of use should an intermittent fault be diagnosed later on.

NOTE: Transmission codes that follow P0894 have set as a result of P0894. Therefore, it is imperative that P0894 be resolved first before attempting to clear additional transmission codes.

Step 2

If the transmission id fitted with a dipstick, check the fluid level as per the instructions in the manual. Top off the level as required or replace the fluid if it is dark in color, has a burnt smell, or has a thick, tarry consistency.

NOTE: Take note that transmission fluid is not consumed like engine like engine oil, and can therefore not “disappear”. Thus, if the fluid level is low, inspect the transmission for fluid leaks, and repair all leaks before continuing the diagnostic/repair procedure.

Step 3

If the transmission fluid is in good condition, there are no fluid leaks on the transmission, and the fluid is up to the proper mark, refer to the manual to determine the correct procedure to follow to test the transmission’s operating pressure at all available testing points. Compare all obtained results with the values stated in the manual; if the tested pressure values are significantly lower than the specified values, suspect a pressure pump failure.

Step 4

If all pressures check out, drain the transmission fluid and remove the oil pan. Inspect the oil pan for the presence of excessive amounts of metal wear particles, or particles that are noticeably bigger than can be reasonably expected. If such large particles or fragments of clutch friction material are found, suspect serious mechanical failures in the transmission; in these cases, the better option is to simply replace the transmission, or to refer the vehicle to the dealer or other competent repair facility for professional assistance.

Step 5

If no excessive wear particles or other debris is found, the only other repair options available to the average non-professional mechanic are to –

Replace the valve body:

Be aware though that while it is possible to do this on a DIY basis, doing this is NOT guaranteed to resolve the problem, because blockages of fluid passages can occur almost anywhere in the transmission.

Test and/or replace shift solenoids and internal wiring:

While defective/inoperable shift solenoids and defective internal wiring can cause code P0894, it very often happens that shift solenoids don’t work because the passages that feed them with transmission fluid are blocked, or are even just partially clogged. Thus, even if all shift solenoids and the transmission’s internal wiring check out and appear to be in proper working order, the code will persist if fluid passages remain blocked.

Replace the transmission:

Replacing the transmission is frequently the fastest and most cost effective way to resolve code P0894. Because of the many possible causes of this code, and the fact that removing, dismantling, cleaning out fluid passages, deciding which components are faulty, replacing them and then reassembling and reinstalling an automatic transmission is generally beyond the capabilities of the average non-professional mechanic.

Codes Related to P0894

There are no codes that are directly related to P0894 – “Transmission component slipping”, although a great many other transmission codes can set as a result of P0894.

BAT Team Discussions for P0894

  • 96 Olds 88 Code P1870
    That code us usually bad news oe internal problems. How is fluid level and condition and filter? You need to get it on a trsnsmission scanner and see where and waht gear and how much the slippage is. Diagnostic Information on DTC P0894 and P1870 #02-07-30-001A - (02/11/2004) Diagnostic Information...