Can I keep driving with P0719?

Usually yes, but don't leave it. The immediate risks are a torque converter clutch that won't release on braking (which can stall the engine as you stop) and brake lamps that may not be working — the second of those is a real safety problem for drivers behind you. Confirm your brake lights work, then get the switch diagnosed.

What is the difference between the "A" and "B" brake switch circuits?

Most brake pedal switches contain two sets of contacts wired as independent circuits. One is normally open and the other normally closed, so the module can verify them against each other — if both read the same state, something is wrong. The "B" circuit is typically the brake-lamp circuit, which also cancels cruise control and releases torque converter lock-up. P0504 is the related code that sets when the two circuits disagree.

Why did my cruise control stop working at the same time?

Because it is the same switch. Cruise control is required to disengage the moment the brake is applied, so it takes its cue from the brake switch. When that circuit reads incorrectly, most vehicles refuse to let cruise engage at all as a safety default. Fixing the switch normally restores cruise control and clears the code together.

Will replacing the brake light switch definitely fix P0719?

It fixes a majority of cases, but not all. Check the fuse and the switch adjustment first — both are free — and inspect the connector for corrosion. If the switch itself is intermittent or the plunger is worn, replacement is the answer; if the fault is a chafed wire in the harness or a bad ground, a new switch will not help. Clear the code after the repair and verify with a test drive that includes highway speed and braking.

OBD-II trouble code

P0719: Torque Converter/Brake Switch "B" Circuit Low

The transmission control system sees an abnormally low voltage on the brake switch "B" circuit — the signal that tells it when your foot is on the brake. The torque converter clutch may refuse to lock up (or refuse to unlock), and cruise control usually stops working.

Medium severityPowertrainTransmission / Torque ConverterDrivable short-term

Quick facts

System: Powertrain
Category: Transmission / Torque Converter
Severity: Medium severity
Drivable: Usually safe to drive short-term
Repair cost range: $0 – $300
DIY difficulty: Intermediate DIY

What does P0719 mean?

Automatic transmissions lock the torque converter clutch at cruising speed to eliminate slip and improve fuel economy. That lock-up must release the instant you touch the brake pedal, or the engine will be dragged down to a stall as the vehicle slows. To know when your foot is on the brake, the powertrain control module (PCM) watches a brake switch circuit — and P0719 says the voltage it sees on the "B" circuit is lower than the module expects.

Most vehicles use a brake pedal switch with two independent circuits, commonly called "A" and "B". One circuit is normally open and one is normally closed, so the module can cross-check them: at any moment, exactly one should be active. The "B" circuit is typically the one that also feeds the brake lamps and cancels cruise control. "Circuit low" means the module measured a lower voltage on that input than it should for the pedal position it believes the switch is in — either the circuit is grounded when it should be at reference voltage, or the switch is reporting the wrong state.

P0719 is a circuit code, not a transmission-internal code. Nothing inside the transmission has to be wrong for it to set. The most common causes are cheap and accessible: a failed or misadjusted brake pedal switch, a blown brake-lamp fuse, corroded connector pins at the switch, or chafed wiring in the harness that runs up the steering column. Because the same switch is shared by the brake lamps, cruise control, shift interlock, and push-button start on many vehicles, a single bad switch can produce a surprisingly wide spread of complaints at once — which is often the clue that points straight at it.

The vehicle is generally still driveable, but treat it as a repair worth doing soon rather than a mild annoyance. If the brake lamps are not working correctly, that is a genuine safety issue for the traffic behind you, and a torque converter clutch that will not release on braking can stall the engine as you come to a stop.

Common causes

Failed brake pedal position switch (the single most common cause)
Misadjusted brake switch — the plunger not making or breaking at the right pedal travel
Blown brake-lamp fuse taking out the circuit's power feed
Corroded or backed-out terminals in the brake switch connector
Chafed or broken wiring in the harness under the dash or along the steering column
Failed brake lamp bulbs or a bad bulb ground on older wiring designs
Poor chassis ground shared by the brake lamp circuit
Failed PCM or TCM input driver (rare — check everything else first)

Symptoms

Check engine light on with P0719 stored
Cruise control will not engage, or drops out on its own
Torque converter clutch does not lock up, hurting highway fuel economy
Engine shudders or stalls when braking to a stop (converter not releasing)
Brake lamps do not illuminate, or stay on continuously
Shifter will not come out of Park on vehicles with a brake-interlock
No obvious symptom at all on some vehicles beyond the stored code

Diagnostic steps

1.Have someone watch the brake lamps while you press the pedal. Lamps that don't light, or that stay lit, point straight at the switch or its fuse.
2.Check the brake-lamp fuse before anything else — it is the cheapest possible fix and it feeds this circuit on most vehicles.
3.Watch the brake switch PID in live data while pressing and releasing the pedal. It should change state cleanly and immediately, with no delay or flicker.
4.Verify brake switch adjustment: the plunger should break contact with only slight pedal travel and fully seat when the pedal is released.
5.Inspect and unplug the brake switch connector. Look for green corrosion, spread terminals, or a pin pushed back into the housing.
6.With the connector off, back-probe for reference voltage on the "B" circuit. No voltage means the fault is upstream; correct voltage means suspect the switch itself.
7.Wiggle-test the harness under the dash and along the column while watching live data — this circuit's wiring flexes with the pedal and column adjustment.
8.Only after the switch, fuse, grounds, and wiring all check good should the module be considered.

Repair cost

$0 – $300

A blown fuse or a switch that only needs readjustment can cost nothing but a few minutes. A brake light switch is typically a $15-$60 part; most shops charge $80-$180 total including diagnosis, since the switch usually sits above the pedal and takes only minutes to swap. Wiring repairs under the dash push the cost toward the top of the range.

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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.