6T40 P0973: Shift Solenoid A Control Circuit Low Causes & Fix

P0973 on a 6T40 is a cleaner code to chase than its performance cousin P0751, as long as you read it for what it is. GM defines it as "Shift Solenoid A Control Circuit Low," and on this unit Shift Solenoid A is the single on/off solenoid that GM's own table calls the Mode 2 solenoid [1]. P0973 is not telling you the transmission shifted wrong. It is telling you the TCM's output driver saw the solenoid circuit pulled to ground when it should not have been. That is an electrical fault, and on a 6T40 the whole circuit lives inside one assembly, the TEHCM.

This guide covers the 6T40 and 6T45 family in the Cruze, Sonic, Malibu, Equinox, Terrain, Encore, Trax, Regal, LaCrosse and their relatives. It covers what GM's monitor checks, why a wiring chase mostly does not apply here, how to test the solenoid on the bench, and how to decide between a solenoid set and a new, programmed module.

Recommended 6T40 parts

A shorted Shift Solenoid A is fixed with a solenoid set, keeping the original TEHCM so no programming is needed. Plan on new gaskets and seals whenever the module comes out. The 7-piece set is for Gen 1 units, so check the TEHCM generation first. Secure checkout.

6T40 Transmission Solenoid Kit, 7-Piece Set (2008-2011)

$111.99View part

6T40 Valve Body Spacer Plate and Gasket Kit GM 24053920

$207.99View part

What GM's monitor actually checks

GM publishes the OBD monitor tables for the 6T40 in its "11OBDG08 TRANS Diagnostics" document, which has a dedicated 6T40 Unique Section. The P0973 entry reads like this [1]:

Three things in that table matter for diagnosis. First, there is no gear, speed, throttle or temperature requirement. The test runs any time the engine has been running for five seconds with normal system voltage, so it can set at idle in Park. Second, nothing disables it. A speed sensor code or an engine code will not keep P0973 from setting, so if it is in memory, the driver really flagged it. Third, it is a one-trip code. The light comes on the first time the fault is present for 1.2 seconds, which is why customers often say the light came on right after a cold start.

The table also explains why P0973 often travels with other codes. In the same 6T40 section, P0973 and P0974 show up in the disable lists of several other transmission monitors [1]. The TCM will not judge clutch, ratio or converter performance when it cannot trust its own solenoid outputs. Fix the circuit code first. The performance codes that come with it often just go away.

What Shift Solenoid A does on a 6T40

The 6T40 runs six pressure control solenoids and one shift solenoid. According to GEARS Magazine, the shift solenoid is an on/off, normally closed solenoid that controls oil to the clutch select valve [2]. That valve decides which clutch a shared pressure control circuit feeds. GM's own PIP6095C solenoid legend names it the Clutch Select (On/Off) solenoid [4]. GM's OBD table names the matching hydraulic part the Mode 2 Multiplex Valve, and the P0751 performance test checks that it moves when 1st Lock is commanded [1].

When the TCM sees a P0973 fault, it can no longer trust that it is driving the clutch select valve. Any function that depends on switching that valve becomes unreliable. What the driver feels depends on the vehicle and calibration. Expect a check engine light at minimum, and possibly reduced shift function while the TCM protects the unit. Do not diagnose from drivability. The code tells you more than the symptoms will.

Why this is not a wiring chase

On older GM units, a solenoid circuit code meant checking a harness from the TCM to a pass-through connector and then to the solenoid. The 6T40 is different. The TCM and solenoid body are one assembly, the TEHCM (transmission electro-hydraulic control module), and the solenoids plug into it. GEARS tells readers to remove each solenoid from the TEHCM before measuring resistance to avoid damaging the module [2]. That tells you the circuit is short and fully inside the transmission. There is no external harness between the driver and the coil.

So a 6T40 P0973 comes down to a short list:

• Shorted Shift Solenoid A coil. A coil with shorted windings reads well below spec and pulls the circuit low. This is the most common cause.
• Terminal or solenoid body short. A cracked solenoid housing, a damaged terminal, or conductive debris across the terminals can ground the circuit.
• Failed output driver in the TEHCM. If the solenoid tests good and the code comes right back, the module's driver is the problem.
• Module supply or ground problems. These are less likely to set this code alone. If P0973 shows up with a group of circuit codes at once, check the TEHCM's power, grounds and connector before you condemn a solenoid.

Diagnosis, in the order I run it

1. Read every code and its status

Write down all stored codes before you clear anything. P0973 alone points at the solenoid or its driver. P0973 with P0751 is still a circuit problem first. A dead circuit cannot move the clutch select valve, and the performance code follows. P0974 instead of P0973 means an open or a short to power, the opposite failure. A group of solenoid circuit codes at once points to module power, ground or the module itself.

2. Check system voltage and software

GM's enable condition needs at least 9 volts [1], so a weak battery will not create this code, but low charging voltage can cause other problems. Check the battery and charging system first. GEARS also recommends checking for TSBs and reflashes on any 6T40 before it comes apart, because some units were pulled for problems a software update fixed [3].

3. Clear and retest at idle

Because the monitor runs with the engine running and has no driving requirement, you can verify quickly. Clear the code, start the engine, let it idle for well over five seconds, and recheck. If P0973 comes back at idle in Park, the fault is hard and the TEHCM is coming out. If it only returns after a heat soak or a long drive, suspect a coil that shorts when hot. Bench test it hot if you can.

4. Check the fluid before you open it up

Check the level hot through the check plug. GEARS gives 85 to 95 C (185 to 205 F) for the hot check [3]. Then pull a sample. Metal in the oil matters for a circuit code too. Fine ferrous debris collects on solenoids, and a new solenoid in contaminated oil will not last.

5. Measure the solenoid on the bench

With the TEHCM out, remove Shift Solenoid A from the module. Do not probe it while installed. GEARS gives 16 to 20 ohms for the shift solenoid and 3 to 5 ohms for each pressure control solenoid [2]. Measure it two ways:

• Across the two terminals: a reading well below 16 ohms means shorted windings. That is your P0973.
• From each terminal to the solenoid body: this should read open. Any continuity to the case means the coil is grounding.

Know which part you are holding. The shift solenoid is the only one in the 6T40 you can energize directly with 12 volts. GEARS warns never to put 12 volts on the pressure control solenoids [2]. Swap the leads and you can ruin a good PCS.

6. Air test it while you are there

A solenoid can pass the resistance check and still stick mechanically. GEARS describes a bench air test at 45 psi with the fluid entry port covered by a plastic plate [2]. Since Shift Solenoid A is normally closed, it should hold air when off and pass it cleanly when you energize it. The factory method uses tool DT 48616 on the control solenoid assembly at 5 Nm (44 lb-in) with 90 to 100 psi of regulated air, commanding each solenoid with a scan tool [3].

7. If the solenoid is good, it is the module

A solenoid that reads 16 to 20 ohms, is open to its case, and switches air correctly cannot set a ground-short flag by itself. If the code comes back with a known-good solenoid installed, the TEHCM output driver is faulty.

The fix

• Shorted Shift Solenoid A, good module: replace the solenoid or the solenoid set and keep the original TEHCM. GEARS points out that reusing the same TEHCM means no reprogramming afterward [2]. Match the generation first. The eighth character of the TEHCM number tells you which you have: 1, 2 or 3 is Gen 1, and B, C or D is Gen 2. The two are not interchangeable [2].
• Failed driver or damaged module: GM services the TEHCM as an assembly, and a new one needs programming. GM's own bulletins show how much the part number depends on the vehicle. PIP4624M listed 2012 Sonic, Cruze 1.8L, Captiva and Orlando with the Gen 1 TEHCM (24256524 at the time), and 2012 Malibu, Equinox, Terrain, LaCrosse, Regal, Verano and Cruze 1.4L with the Gen 2 TEHCM (24265367) [5]. Those numbers have been superseded since, so order by VIN.
• 2025-2026 Trax or Envista: check PIP6095C before you order anything. It covers a solenoid screen condition on those builds, lists the control solenoid valve and TCM assembly 24052399 and gasket and harness seal kit 24053920, and allows 3.0 hours for the job [4]. It is written for a harsh shift into Drive, not P0973, so use it for parts and procedure only if your vehicle is covered.
• Gaskets: plan on a new side cover gasket and filter seal whenever the TEHCM comes out. Reusing a gasket on this job causes comebacks.
• After any repair: refill with DEXRON VI. GM's 2026 TechLink capacity chart lists the current 6T40 at 4.0 to 6.0 liters (4.2 to 6.3 quarts) [6]. Check the level hot. Clear codes, idle past the five-second enable, then road test and confirm the DTC status reads "test passed" before the car leaves.

FAQ

What does P0973 mean on a 6T40?

GM defines it as Shift Solenoid A Control Circuit Low. The TCM's hardware reported a low voltage, or ground short, on the Mode 2 shift solenoid circuit for 1.2 seconds out of a 1.5 second sample. It is a one-trip code, so the check engine light comes on the first time it fails.

Is P0973 the solenoid or the TCM?

On a 6T40 it is one or the other, because the solenoid plugs into the TEHCM and there is no external harness between them. Remove the solenoid and measure it. If it reads well under 16 to 20 ohms or has continuity to its case, it is the solenoid. If it tests good and the code comes back, the module driver has failed.

What is the difference between P0973 and P0974?

P0973 is a low or ground-short fault on the Shift Solenoid A circuit and sets in one trip. P0974 is a high fault, meaning an open circuit or a short to power, and needs two trips. Both use the same 1.2 second fail timer in GM's table.

Do I have to program the TCM to fix P0973?

Only if you replace the TEHCM. If the shift solenoid is the problem, replacing the solenoid or solenoid set and reusing the original module avoids programming. Match the TEHCM generation first, because Gen 1 and Gen 2 parts are not interchangeable.

What fluid does the 6T40 take after the repair?

DEXRON VI. GM's 2026 TechLink capacity chart lists 4.0 to 6.0 liters (4.2 to 6.3 quarts) for current 6T40 applications. Check the level hot through the check plug at 85 to 95 C (185 to 205 F).