Why does a transmission code make my engine stall?

Because on many vehicles the third pressure control solenoid meters torque converter clutch apply, and a low-side fault can drive that clutch to full lock and hold it there. A locked converter clutch bolts the engine solidly to the transmission input, so slowing to a stop drags the engine down exactly as it would in a manual car left in gear with your foot off the clutch. The engine itself is healthy; it is being stalled by the driveline.

Is there a test I can do myself before booking it in?

Yes, and it costs nothing. Next time you approach a junction, coast to a halt with the selector in neutral. If the engine survives the stop in neutral but dies when you come to a stop in drive, the engine is not the problem and something in the driveline is refusing to release. That single observation is worth more to the workshop than a list of symptoms, and it stops them spending your money on idle control and fuel diagnosis.

Could I have this code and no stalling at all?

Quite possibly. Two things change the picture. Some manufacturers build these solenoids inverse-proportional, so more current means less pressure and a low-side fault leaves you with no lockup instead of permanent lockup. And many modules protect their own output stage by switching it off as soon as they detect the short, in which case the solenoid never applies anything. Both give you a stored P0970 with a car that drives more or less normally, and both still need the same wiring diagnosis.

Can I keep driving with P0970?

This is one of the few transmission codes where the honest answer is no, and the reason is safety rather than mechanical damage. An engine that dies every time you come to a stop will do it in traffic, at a junction, or partway across one, and once it dies you lose power steering assist and vacuum assist to the brakes at the worst possible moment. If your car is stalling on the approach to stops, have it recovered rather than driven. If it is not stalling — see the previous answer, since not every vehicle with this code does — it is safe enough to drive to a workshop promptly.

OBD-II trouble code

P0970: Pressure Control Solenoid "C" Control Circuit Low

A low-side fault on the third pressure control solenoid. Where that circuit meters torque converter apply, the classic complaint is not a bad shift at all — it is an engine that dies every time you roll up to a junction, which sends most people looking at the wrong system entirely.

High severityPowertrainTransmission / Pressure ControlDo not drive

Quick facts

System: Powertrain
Category: Transmission / Pressure Control
Severity: High severity
Drivable: No — stop driving until repaired
Repair cost range: $130 – $1,600
DIY difficulty: Shop recommended

One of 27 pressure control solenoid codes

P0970 sits in a grid: one axis is which solenoid the letter refers to, the other is what went wrong with it. Each cell is a genuinely different fault with its own diagnosis — but codes from the same row or column often appear together, and what a pairing means is usually the fastest way in. The hub page lays out all 27 and explains how to read them against each other.

See all pressure control solenoid codes →

Browse every code in P0900–P0999, or start from the full code library.

What does P0970 mean?

P0970 tells you the module saw an abnormally low voltage on the control side of the third pressure control solenoid — in practice a path to ground that should not exist, or a coil drawing far more current than the driver expects to see. That is a plain electrical statement and it is the same statement the equivalent codes for the 'A' and 'B' circuits make. What is not the same is the consequence, and the consequence is entirely about what the third solenoid happens to control.

On a large proportion of conventional automatics the 'C' circuit meters torque converter clutch apply pressure. That single fact reorganises this page. On the common design where rising solenoid current raises apply pressure, an unwanted path to ground drives that circuit toward maximum — the converter clutch is pushed toward full lock and stays there. A locked converter clutch is a mechanical connection between the engine and the transmission input. It is exactly like sitting in a manual car in gear with your foot off the clutch pedal: the car will drive, and then it will stall the moment you slow to a stop. Drivers describe an engine that dies at every junction, a shudder or lurch as they brake to a halt, and an engine that restarts and behaves perfectly until the next stop.

That matters more than the inconvenience, because almost nobody diagnoses it as a transmission fault. The complaint is 'it stalls', so the idle control, the fuel system, the throttle body and the mass airflow sensor all get looked at before anyone reads a transmission code. There is a free test that settles it in one stop: as you coast to a halt, put the selector in neutral. If the engine survives the stop in neutral and dies in drive, the engine is fine and something in the driveline is refusing to let go. That test costs nothing, takes one junction, and it points at this circuit before a single connector is opened.

Two honest caveats keep this from being a rule. First, the direction of the pressure characteristic is a design decision, and not every manufacturer builds these solenoids the same way; some are inverse-proportional, so more current means less pressure and a low-side fault produces the opposite symptom — no lockup rather than permanent lockup. Establishing which type the vehicle uses before predicting the symptom is worth the five minutes it takes. Second, many modules protect their own output stages: if the short is hard enough, the driver is switched off almost immediately, in which case the solenoid never gets to apply anything and the car simply loses lockup while storing the code. Both outcomes are consistent with P0970, and which one you get depends on the module, not on the wiring.

On the repair side the useful news is that a low-side fault is provable with the vehicle switched off. With the transmission case connector unplugged, measure resistance from the solenoid control pin to a clean chassis ground. A healthy control circuit is isolated from ground except through the coil path the manufacturer specifies; a reading near zero from a pin that should be isolated tells you the fault is in the wiring or the solenoid rather than in the module, and it tells you that before anything is dismantled or bought.

Common causes

Control wire chafed through to the transmission case, a bracket or the subframe
Solenoid 'C' with shorted windings drawing excessive current
Water or fluid intrusion into the transmission case connector bridging pins to ground
Damaged internal harness inside the transmission rubbing on a rotating part
Corroded terminal in the case connector making contact with the shell
Wiring pinched during a previous transmission, subframe or exhaust repair
Failed output driver in the transmission control module holding the circuit low
Rodent damage to the harness section running along the transmission
Aftermarket or incorrectly specified solenoid with the wrong coil resistance

Symptoms

Engine stalls as the vehicle comes to a stop, then restarts and runs normally
Shudder or lurch through the car in the last few miles per hour before a halt
Engine survives the stop if the selector is moved to neutral
Very low engine speed at low road speeds, as though the car is over-geared
Transmission dropping into a failsafe mode and refusing to change gear normally
Torque converter clutch showing as commanded off but engine and input shaft speed still locked together
Check engine light stored with the transmission warning lamp on some vehicles
Fault present from the moment the engine starts rather than appearing after warm-up

Diagnostic steps

1.Ask whether the engine dies specifically when coming to a stop in gear, and have the driver try coasting to a halt in neutral — surviving in neutral and stalling in drive points at the driveline, not the engine.
2.Establish from documentation what the 'C' circuit controls on this transmission and whether its pressure characteristic rises or falls with current, before predicting any symptom.
3.With the ignition off and the transmission case connector unplugged, measure resistance from the solenoid control pin to a clean chassis ground; a near-zero reading on a pin that should be isolated proves the fault is outside the module.
4.Measure the solenoid coil resistance at the case connector and compare it against the manufacturer's figure to separate a shorted winding from a shorted wire.
5.If the resistance checks are clean with the connector unplugged, the module side becomes the candidate and the code should be rechecked with the transmission disconnected.
6.Inspect the external harness where it crosses the case, brackets and the subframe, and look for the shiny witness mark that a chafe leaves before it becomes a short.
7.Check the case connector seal and pins for fluid or water, which bridges pins to the earthed connector shell.
8.Compare engine speed against input shaft speed on a scan tool at low road speeds to confirm whether the converter clutch is mechanically locked.
9.Review whether any recent work disturbed the transmission harness, since a pinched wire from an unrelated repair presents exactly like a failed solenoid.

Repair cost

$130 – $1,600

Diagnosis is $120 to $250, and on this code a competent shop should reach a verdict quickly because the key resistance test needs no power and no dismantling. A chafed external wire repair is $130 to $400 and is a common and genuinely cheap outcome. A case connector or terminal repair is $180 to $450. Solenoid replacement where the third solenoid sits in the valve body is $650 to $1,500 fitted, including the fluid and filter the job requires. A damaged transmission control module output is the expensive branch at $600 to $1,600 with programming. Note that stalling repeatedly at junctions is a driving hazard rather than a wear problem, so the cost that matters most here is not mechanical.

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DIY vs shop

Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.