P0990 Code: Transmission Fluid Pressure Sensor/Switch E Circuit High

What the P0990 code means

Modern automatic transmissions measure fluid pressure in several circuits to confirm that each clutch actually receives pressure when its solenoid is commanded on.

The sensor gets a 5 volt reference and a ground from the computer and sends back a signal somewhere between about 0.5 and 4.5 volts. The P0990 code is a high signal, which is usually caused by an open circuit or an interrupted ground.

When the signal fails, the computer cannot confirm that the clutches are applying, and it usually puts the transmission in limp mode. On any transmission code, check the fluid first. The level has to be right using the manufacturer procedure, which often calls for the engine running at a specific temperature. The fluid should be red or pink and should not smell burnt. Low or worn fluid causes slipping, harsh shifts and solenoid or gear ratio codes that go away once the fluid is corrected.

To confirm the diagnosis, measure the continuity of each wire between the component connector and the computer connector with the key off. It should be under 1 ohm, and an infinite reading means the wire is open. If the wiring checks out, measure the component itself: infinite resistance confirms that it is open inside.

P0990 code symptoms

• Check engine light on.
• Transmission in limp mode.
• Harsh shifts or no shifts at all.

Likely causes of the P0990 code

1. Loose or broken connector. The most frequent cause.
2. Signal or ground wire cut. The signal rises all the way to the reference.
3. Sensor open inside, with infinite resistance.
4. Short to 5 volts or 12 volts from rubbing against another wire in the harness.

How to diagnose the P0990 code step by step

1. Read the sensor value on the scan tool and compare it with what you expect.
2. Inspect the connector for corrosion, water or loose pins.
3. Check power and ground with the key on: the reference should be correct and the voltage drop on the ground should be under 0.1 volt.
4. Measure the signal with the connector plugged in and see whether it changes with the condition.
5. Do a wiggle test on the harness with the scan tool in graph mode.
6. Check the continuity of each wire to the computer. It should be under 1 ohm.
7. Check the fluid level and condition.

How to fix the P0990 code

• Repair the connector or the wiring.
• Replace the sensor if the tests confirm it is bad.
• Correct the real condition if there is one.
• Clear the codes and verify the repair with a road test.

Technical reference data

• 5 volt sensor or pressure switch.
• These values are only a guide, so look up the manufacturer data for your vehicle.

Brand-specific notes

Check the service manual to see which pressure circuit matches the letter E on your transmission, because the lettering is not the same from one transmission to the next.

Frequently asked questions about P0990