I have circuit low codes on both banks. Is that two shorts?

Very unlikely. Two independent wires chafing through to ground at the same time is a coincidence; a single failure affecting both is not. The two most probable explanations are a wire-to-wire short between the two control circuits, which drags whichever output is currently off down toward the other, and a common failure point — a shared connector full of water, a corroded splice, or a module output stage that took both drivers down. Test the shared parts of the circuit before testing either branch.

The code only shows up when it rains. What does that mean?

It means you are looking for water rather than for damage. Moisture bridging terminals inside a connector is a genuine short to ground while it is there and completely absent once it dries, which is why continuity tests on a dry day find nothing. On transverse V engines the rear-bank harness sits below the cowl, so blocked cowl drains and a failed windscreen seal send water straight onto it. Open the connector, look for staining and corrosion, clear the drains, and re-seal rather than chasing the wire.

How is this different from the Bank 1 circuit low code?

Electrically they describe the same condition, but the physical search differs. The Bank 1 harness typically runs across the top of the manifold, where the usual cause is a wire pinched or re-routed during other engine work. The Bank 2 branch on a transverse engine runs along the back of the engine under the cowl, where the usual causes are water and heat rather than mechanical disturbance. The two-bank layout also adds a possibility Bank 1 alone does not have: the two control wires shorting to each other.

Should I replace the actuator?

Not before you have proved the wiring is clean. A short to ground on a control output is more often a harness or connector problem than a component problem, and a new actuator plugged into a shorted circuit sets the code again immediately — and can damage the module driver a second time. Measure the winding resistance and check for continuity between each winding terminal and the actuator body; if both are normal, the fault is outside the component.

OBD-II trouble code

P2012: Intake Manifold Runner Control Circuit Low (Bank 2)

The Bank 2 runner control circuit is being pulled toward ground. On a two-bank system the ground it has found is not always the chassis — the neighbouring bank's own control wire is a real possibility.

Medium severityPowertrainAir Intake / Manifold ControlDrivable short-term

Quick facts

System: Powertrain
Category: Air Intake / Manifold Control
Severity: Medium severity
Drivable: Usually safe to drive short-term
Repair cost range: $100 – $700
DIY difficulty: Intermediate DIY

What does P2012 mean?

On a single-bank engine a circuit low fault has one shape: a conductor has found a path to ground. On a two-bank engine there is a second shape, and it is the one people miss.

The two runner control wires leave the module side by side. They are usually adjacent pins in the same connector, they usually travel together in the same loom for most of their length, and on many vehicles they pass through a shared bulkhead grommet or a common splice pack before dividing. Insulation that breaks down between two neighbouring wires connects them to each other, not to the body. And when one output is commanded on while the other is off, a wire-to-wire short between them looks exactly like a short to ground from the point of view of whichever driver is currently switched off — its line is being dragged down by its neighbour.

That gives this code a test that a single-bank circuit low code has no use for. Disconnect both actuators and both ends at the module, then measure continuity between the Bank 1 and Bank 2 control wires. Any reading at all is the answer, and it explains what would otherwise be a confusing symptom set: codes that alternate between banks, or a fault that only appears when the runners are commanded to move rather than at key-on.

The same logic applies to code pairings. If P2009 and P2012 are both stored — circuit low on both banks — a coincidence of two independent shorts is implausible. What is likely is either one wire-to-wire short between the two circuits, or a common point that has failed: a shared connector flooded with water, a splice corroded inside the loom, or a module driver stage that has taken both outputs down together. Look at what the two circuits share before looking at either one alone.

The Bank 2 branch also has a moisture story of its own. On transversely mounted V engines the rear bank's harness runs along the back of the engine, below the cowl and windscreen scuttle. Every leaf, every blocked cowl drain and every failed windscreen seal sends water down that path. Water sitting in a connector is a slow, reversible short to ground: the code appears in wet weather, disappears in dry weather, and no amount of continuity testing on a sunny afternoon will reproduce it. If the fault correlates with rain or with washing the car, clear the cowl drains and open the connectors before opening the loom.

As elsewhere in this block, expect the module to protect its driver by shutting the output down, which drops the flaps to their sprung open position and produces a Bank 2 stuck-open code alongside. That is the module reporting its own reaction, not a second failure.

Common causes

Insulation breakdown between the Bank 1 and Bank 2 control wires where they run together
Control wire shorted to a grounded bracket, bolt or heat shield on the Bank 2 branch
Water intrusion into the rear-bank connector from blocked cowl or scuttle drains
Corroded splice inside the loom where the runner control circuit divides between banks
Internal short to ground within the Bank 2 actuator or solenoid winding
Terminal displaced in the connector body and touching the metal shell
Module output driver damaged by a sustained short

Symptoms

Check engine light on
Commonly accompanied by a Bank 2 stuck-open code such as P2005
Fault that appears in wet weather or after washing and clears when everything dries out
Codes that appear to alternate between the two banks over time
Weak low-speed torque once the module disables the affected output
Often no symptom the driver notices

Diagnostic steps

1.Ask whether the code correlates with rain, washing or a particular season. A weather-linked intermittent points at moisture in a connector rather than at a chafed wire, and those are found by opening connectors, not by continuity testing on a dry day.
2.Disconnect both bank actuators and the module connector, then measure continuity between the Bank 1 and Bank 2 control wires. Any continuity at all identifies a wire-to-wire short and explains alternating or paired codes.
3.With everything still disconnected, measure continuity from each control wire to chassis ground. A reading confirms a conventional short and localises the search to points where the loom touches metal.
4.Inspect the rear-bank connector for water staining, green corrosion and a heat-brittled lock. Check the cowl and scuttle drains above it while you are there.
5.Measure resistance across the Bank 2 actuator winding and from each terminal to the component housing. A winding shorted to its own case produces this code with perfect wiring.
6.Trace the Bank 2 branch along heat shields, brackets and any point where it is clamped, looking for flattened insulation and shiny rub marks.
7.If both banks show circuit low codes, stop testing the branches and examine what they share — the common connector, the splice pack and the module output stage.
8.Repair, clear all codes including any stuck-runner code stored alongside, then complete a drive cycle in conditions similar to those that set the code.

Repair cost

$100 – $700

Drying and repairing a corroded connector is often $100 to $250. Opening the loom to repair a wire-to-wire short is $150 to $400 depending on how much of the harness has to be unwrapped and how buried the section is. A shorted solenoid is $120 to $300 installed; an actuator on the rear bank of a transverse V engine $300 to $700 with the access it requires.

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DIY vs shop

This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.