P0077
PowertrainIntake Valve Control Solenoid Circuit High (Bank 1)
The ECU watches the voltage on the wire that feeds the intake valve control solenoid on bank 1, the part that lets the engine shift its variable valve timing. When that voltage reads too high for what the ECU expects, it logs P0077. For you as the driver, it means the engine's clever timing system isn't being controlled properly, usually down to a wiring or solenoid fault rather than a worn-out engine.
ⓘ Information only. This page provides general educational information about fault code P0077. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0077 mean?
P0077 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Intake Valve Control Solenoid Circuit High (Bank 1).
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Engine warning light on the dash, sometimes the only thing you notice
- • Lumpy or uneven idle, often worse once the engine has warmed through
- • A flat spot or hesitation when you put your foot down, commonly around 2,000 to 3,500 rpm
- • Noticeably worse fuel economy on your usual runs
- • Throttle feels lazy, like the engine isn't keen to pick up
- • Occasional misfire or shudder that comes and goes
Possible causes
Causes commonly associated with P0077, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. A short to battery voltage somewhere in the solenoid wiring, which is exactly what pushes the reading too high. This is the classic cause of a 'circuit high' code
- 2. Corroded or moisture-affected connector at the solenoid. These sit low in the engine bay and cop a lot of road spray and heat
- 3. Wiring between the ECU and solenoid chafed, pinched, or rubbed through against a bracket
- 4. The intake valve control solenoid itself failed or shorted internally
- 5. Oxidised or spread connector pins giving a poor contact and odd voltage spikes
- 6. Faulty ECU output driver. Rare, and you only land here once everything else checks out
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Read the live data and freeze frame with a scanner. Note what the engine was doing when it logged, and check for cam timing or other timing codes stored alongside it
- 2. Get the connector off the solenoid and inspect it properly. Look for green corrosion, water, bent pins, and follow the loom back for any chafing against the block or a bracket
- 3. Back-probe the solenoid feed wire with a multimeter at idle and under a bit of load. You're looking for the expected signal voltage, often in the 4.5 to 5.5V region depending on the system
- 4. With the connector unplugged, measure the solenoid coil resistance and compare to spec, usually somewhere around 2.5 to 3.5 ohms. Out of range means the solenoid is your problem
- 5. Disconnect the ECU and check whether the solenoid wire is seeing full battery voltage. If it is with the ECU out of circuit, you've got a short to power in the loom
- 6. If the wiring, connector, and solenoid all test fine, then and only then start looking at the ECU driver
Common questions about P0077
Can I keep driving the car like this? +
Short trips won't strand you, and many cars drop into a safe timing position so they still run. But the timing system isn't doing its job, so you'll feel it as poor pulling and worse economy, and a constant misfire can wash oil down the bores over time. Fine to get it home or to a garage, not something to leave for months.
Is this going to cost me an MOT pass? +
The code on its own isn't a fail. What the tester sees is the engine warning light. If the MIL is lit when the car goes on the ramp, that's an emissions-related fail in itself, regardless of what the code is. Fix the fault, clear it, and let the light stay off through a few drive cycles before you book the test.
What am I likely to pay to sort it? +
Depends entirely on the cause. A connector clean or a small wiring repair at an independent might be £40 to £90. A new solenoid plus fitting at a decent local garage tends to land in the low hundreds, call it £120 to £300 with parts and labour. A main dealer will charge more, and in the rare case it's the ECU driver you could be looking at the high hundreds once programming is added in.
How do I tell whether it's the wiring or the solenoid itself? +
Do it in order. Unplug the connector first and look for corrosion or water, because a manky connector or a chafed wire is more common than a dead solenoid and costs almost nothing to fix. Then ohm out the solenoid coil with the plug off. If the resistance is way off the spec, the solenoid is gone. If the coil reads fine but the wire is seeing battery voltage with the ECU unplugged, your fault is a short in the loom, not the part.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →