A Mazda with the “SKYACTIV” FW6A-EL transmission uses pressure switches to monitor the clutch application. When engagement pressure is supplied to the applicable clutch and brake, the oil pressure switch contact point closes. The TCM detects that clutch engagement pressure is supplied to the clutch/brake by opening/closing the oil pressure switch contact point.
There have been a number of these vehicles experiencing a complaint of the “Check Engine” and “A/T Warning” Lamps illuminated with the following trouble codes stored in TCM memory:
P0842 – Oil Pressure Switch #1 (pressure switch B) Stuck ON;
P0847 – Oil Pressure Switch #2 (pressure switch A) Stuck ON;
P0872 – Oil Pressure Switch #3 (pressure switch A) Stuck ON;
P0877 – Oil Pressure Switch #4 (pressure switch B) Stuck ON;
P0780 – Gear Shifting Malfunction; and
P1738 – Automatic Transmission Internal Malfunction.
This problem can be caused by contamination getting into the oil pressure switches mounted on the valve body. Although it seems that this setup is susceptible to this condition setting these codes, based on the limited amount of contamination observed, it suggests that the TCM software may be overly sensitive to setting these pressure switch codes.
From the help given on the ATSG tech line, after programming the A/T Control Module with the latest software updates, these codes do not seem to set so quickly. This, however, does not apply to vehicles that are exhibiting any transmission problems such as delayed engagements. All transmission malfunctions must be diagnosed and repaired before updating the A/T Control Module with the latest software updates.
If pressure switches are needed, the oil pressure switch A manifold can be purchased using part number FZ01-21-2C0, while pressure switch manifold B can be purchased under part number FZ01-21-2J0. And FZ01-21-500 for a new transmission oil filter.
When working on this, use caution when removing Oil Pressure Switch Manifold “A” to avoid damaging the ATF Temperature Sensor.
The following vehicles seem to be susceptible to this condition:
2012 – 2013 Mazda3
2014 – 2018 Mazda3 (Japan Built with VIN starting with JM1)
2014 – 2018 Mazda3 (Mexico Built with VIN starting with 3MZ)
2013 – 2018 CX5
2014 – 2018 Mazda6
2016 – 2018 CX3
2016 – 2018 CX9
This article courtesy of Transmission Digest.