A P0770 trouble code is related to a vehicle’s automatic transmission and the shift solenoid that controls the lock-up mechanism of the torque converter.
What the P0770 code means
P0770 is an OBD-II generic code for a malfunction of shift solenoid E on the transmission valve body. This controls the supply of hydraulic pressure to the lock-up clutch of the torque converter that creates a one-to-one ratio for both input and output transmission speeds. Lock up typically happens at cruising speeds when the torque converter doesn’t need to slip and to increase highway fuel economy.
What causes the P0770 code?
The most common causes for a P0770 are:
- Faulty transmission shift solenoid E
- Faulty transmission shift solenoid wiring harness
- Leaking, low, or dirty transmission fluid
- Faulty torque converter
- Damaged transmission
What are the symptoms of the P0770 code?
The most common symptoms of a P0770 include the transmission’s refusal to engage lock up, decreased fuel economy, and higher engine speeds while cruising. In some cases, the transmission will shift harshly or stall the engine when idle. In others, nothing more than a check engine light will illuminate on the dash.
How does a mechanic diagnose the P0770 code?
Because a P0770 is related to a vehicle’s speed, your mechanic will first test drive the vehicle with the check engine light to see how severe the symptoms are. If the vehicle seems to be operating as it should, the code could be an intermittent issue. If it fails to enter lock up however, your mechanic will monitor the engine speed, road speed and throttle position to confirm the transmission isn’t locking up the torque converter.
By using a professional OBD-II scanner, your mechanic can monitor solenoid E’s signal to determine if it is working as it should. If not, the solenoid will be replaced. However, if the solenoid is sending the correct signal range depending on throttle position, there is likely a mechanical problem with the torque converter, meaning it will have to be replaced.
As with most transmission trouble codes, the fluid will be checked for being low or dirty.
Common mistakes when diagnosing the P0770 code
Low, or dirty transmission fluid can cause a number of unwanted issues and can even result in diagnostic trouble codes. It’s critical to check the fluid before purchasing replacement parts.
How serious is the P0770 code?
Because most P0770s will impact how the torque converter locks and unlocks, it’s likely that your transmission could be at risk of overheating with this code. It’s important to get this inspected as soon as possible and if you do have to drive with a P0770, try to avoid highway speeds.
What repairs can fix the P0770 code?
The most common repairs for a P0770 are as follows:
- Replacing the shift solenoid E
- Repairing damaged wiring or electrical connectors
- Replacing the torque converter
- Flushing and changing transmission fluid
Additional comments for consideration regarding the P0770 code
Toyota issued a factory service bulletin for the P0770, impacting the 2003 Corolla and Matrix.
Need help with a P0770 code?
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