Wiring fault in the solenoid circuit, such as a short to a power supply, chafed insulation or a damaged loom; Corroded, loose or damaged connector at the intake valve control solenoid; Faulty intake valve control solenoid with an internal electrical fault; Poor power or earth supply to the solenoid circuit, or a blown or incorrect fuse where fitted; Engine oil contamination or oil leaking into the solenoid connector and wiring; Faulty driver circuit inside the engine control unit; Outdated or faulty control unit software, where the manufacturer has issued a fix for this code on the engine concerned.

P0077

Intake Valve Control Solenoid Circuit High Bank 1.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
0: AreaFuel and air metering, auxiliary emission controls
77: FaultThe specific fault in that area

What it means

P0077 is the generic code for an Intake Valve Control Solenoid Circuit High on Bank 1. The engine control unit monitors the electrical circuit of the solenoid that controls intake valve timing or lift, and it saw a voltage higher than expected, such as a short to voltage or a fault in the driver. The exact system (variable valve timing, variable lift or similar) and the monitoring method depend on the engine.

Symptoms

Engine warning light on
Rough or unstable idle
Reduced power or flat acceleration
Poor fuel economy
Hesitation or stalling at low speed
Engine may enter a limited performance mode

Possible causes

Wiring fault in the solenoid circuit, such as a short to a power supply, chafed insulation or a damaged loomlikely
Corroded, loose or damaged connector at the intake valve control solenoidlikely
Faulty intake valve control solenoid with an internal electrical faultlikely
Poor power or earth supply to the solenoid circuit, or a blown or incorrect fuse where fittedpossible
Engine oil contamination or oil leaking into the solenoid connector and wiringpossible
Faulty driver circuit inside the engine control unitrare
Outdated or faulty control unit software, where the manufacturer has issued a fix for this code on the engine concernedrare

How to diagnose

Read all stored and pending codes and note the freeze frame data (engine speed, load, temperature) to see when the fault set
Check the engine oil level and condition, as valve timing systems depend on correct oil
Inspect the solenoid connector and the wiring back along the loom for oil, corrosion, chafing, heat damage or pushed-out pins
Check the relevant fuse and the power and earth supply at the solenoid connector against the wiring diagram for the engine
Measure the solenoid coil resistance and compare it with the manufacturer's specification for that engine
With the connector unplugged, check the control wire for a short to voltage and for continuity back to the control unit
Use a scan tool that supports actuator tests to command the solenoid and watch for a response and for the signal to match the command
Check for any manufacturer bulletins or software updates applicable to the engine and code

How to fix

Repair or replace the damaged wiring, and secure the loom away from heat and rubbing
Clean, repair or replace the corroded or damaged connector and terminals
Replace the faulty intake valve control solenoid, and clean or replace its seals as the engine design requires
Restore the correct power or earth supply, and replace the fuse after finding why it failed
Correct oil leaks into the connector, change the oil and filter if it is dirty or incorrect
Replace or repair the control unit only after the wiring and solenoid have been proven good, and apply any manufacturer software update if it is a known cause

Can I keep driving?

Medium severity

The car can usually be driven carefully for a short time, but fix it soon as it may run poorly, use more fuel and could worsen. Avoid hard driving, and stop if the engine runs very roughly or loses power badly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.