722.6 Conductor Plate
Replacement Cost

A customer pulls into the lot in an E320 or a Grand Cherokee, tells you the car "just quit shifting" at a light, and the engine is screaming at 3,500 RPM doing 45 mph. Nine times out of ten that is not a broken transmission. It is a $250 electronic plate bolted to the inside of the valve body, and the two speed sensors molded into it have gone open circuit.

This unit is the five-speed Mercedes built from the mid-1990s through the late 2000s, and the same hardware went into a lot of Chrysler-family vehicles as the NAG1: Grand Cherokee WK, Commander, Charger, 300, Magnum, Challenger, Sprinter. The conductor plate is the nervous system. It carries the shift solenoid wiring, the N2 and N3 turbine speed sensors, and the output speed sensor, all molded into one flat plastic-and-copper assembly that lives in ATF at 200 degrees F for its entire life. Heat cycles crack the molding, the sensor windings open up, and the module loses the signal it needs to control the shift.

How It Actually Fails

The speed sensors open up

The N2 and N3 sensors are the ones that quit first. When the module loses one, it can no longer confirm what gear the unit is actually in, so it defaults to limp: second gear on a Mercedes, second or third on most NAG1 applications, with no torque converter lockup and no downshift back to first. The driver says the car "won't shift out of one gear" and that it started with zero warning. That abruptness is the tell — mechanical failures announce themselves over weeks with slipping and flare, a dead conductor plate shows up in one instant.

Early failures are intermittent and heat-sensitive. The car drives fine for twenty minutes, drops into limp, and then a key cycle after a cool-down brings it back. Anyone who has chased this knows that pattern: the crack in the molding opens as the plate expands. Once it fails cold too, the plate is fully open.

The 13-pin connector sleeve leaks

This is the failure that turns a cheap job into an expensive one. The plate exits the case through a 13-pin connector on the side, and inside that connector is a plastic sleeve with two small O-rings. Those O-rings shrink and harden with age, and ATF then wicks up the inside of the wiring harness by capillary action — uphill, slowly, over months — straight into the transmission control module.

The owner sees a red drip on the driveway that everyone blames on the pan gasket. What is actually happening is fluid pooling in the module housing, corroding pins and eventually killing the TCM. Replace a plate without replacing that sleeve and you are doing the job twice. If the connector plug already smells like ATF when you pull it, budget for the module too — feeding a new plate from a soaked, corroded module is the number one reason people report a brand new conductor plate that failed in a week.

Solenoid circuit faults on the same plate

The shift solenoids bolt to the plate and share its printed circuitry, so a cracked trace produces a solenoid electrical code with a perfectly good solenoid on the end of it. Ohm the solenoid at its own terminals before replacing anything; both the shift and pressure regulating solenoids read in the low single digits of ohms. In spec at the solenoid but still an open circuit at the module means the fault is in the plate.

The Codes You Will Pull

• P0715 — input / turbine speed sensor circuit. On this unit that is the N2 or N3 sensor in the plate. Detail on the generic code is in our P0715 guide.
• P0720 / P0722 — output speed sensor circuit, no signal. Second most common code here.
• P0717 — turbine speed sensor no signal. Same plate, same fix.
• P0731 through P0735 — incorrect gear ratio in a specific gear. These often set alongside the speed sensor codes because the module is comparing ratios it can no longer measure.
• P0700 at the engine module — a pointer only. You need a scan tool that talks to the transmission module directly to read the real fault. A generic reader will leave you guessing.
• Mercedes-specific stored faults in the 2-7xx range for N2/N3 implausible signal. If the shop has factory-level software, this is where the answer is.

What to Check Before Buying a Plate

• Pull the 13-pin connector and look inside. Dry means plate and sleeve. Oily means plate, sleeve, and a hard look at the module. Sixty seconds of inspection decides a $600 difference.
• Check the fluid level correctly. This unit fills through a tube with a dedicated dipstick most cars did not come with, and it is checked hot with the engine running. Low fluid produces harsh shifts and ratio codes that mimic a bad plate.
• Load test the battery and check charging voltage. These modules are voltage sensitive; a tired battery on a cold morning sets an armful of transmission electrical codes that clear once the charging system is right.
• Look at the pan and the magnet. Clean fluid and fine paste on the magnet means the unit is healthy and worth fixing. Hard metal or friction chunks means the plate is a symptom, not the cause.
• Check whether it downshifts manually. If the selector into 2 gives you a real second gear with proper feel, the mechanical side is intact and you are chasing electronics.
• Confirm the part number. Mercedes and Chrysler-badged NAG1 plates are not universally interchangeable across the production run. Match by VIN or by the number stamped on the old plate. The NAG1 limp mode fix page runs the same decision tree from the Jeep and Dodge side.

722.6 Conductor Plate Cost Breakdown

The whole job is done from underneath with the transmission in the car. Pan down, filter out, valve body unbolted and lowered, plate unclipped, new plate in, sleeve replaced, torque everything to spec and refill. It is genuinely a Saturday job for someone with a lift, jack stands and patience — the hard part is the fluid fill procedure, not the wrenching.

Fix It, or Walk Away From the Unit?

Fix it, without hesitation, when the failure was electronic and the mechanical side is clean — the overwhelming majority of these cars. A $750 plate job on a Grand Cherokee or an E-Class that otherwise drives well is one of the best returns in the repair business. Do the plate, the sleeve, the filter and a full fluid service in one visit.

Think harder when the plate is only part of the story. Burnt fluid, a magnet loaded with friction material, or months of driving in limp mode all mean the clutch packs have been cooking. Limp holds maximum line pressure and leaves the converter unlocked, pumping heat straight into the fluid; six months of that takes out the K1 or B2 pack. There, the plate buys you a car that shifts briefly before a rebuild follows.

Go to a rebuild or reman when you have a dead plate plus mechanical evidence: slip under load in a specific gear, a flare between gears, or metal in the pan. You are paying for a teardown either way, and a rebuilt unit with a new plate and updated sleeve beats serial partial repairs. The 722.6 problems and cost and NAG1 solenoid replacement cost pages cover the rest of the unit.

Whatever you do, use the correct fluid — this unit is fussy, and the wrong ATF causes shudder and harsh engagement within a few hundred miles. Our fluid guide for the NAG1 and 722.6 lists the specs that apply. The same discipline pays on the other imports in this class: the 09G / TF-60SN guide and the U660E problems and cost page.

FAQ

How much does a 722.6 conductor plate cost to replace?

The plate itself runs about $180 to $420 depending on brand and whether it includes the connector sleeve. Shop labor is typically 2.0 to 3.5 hours, so most independent shops land between $550 and $1,100 all in. A Mercedes dealer will usually quote $1,200 to $1,900 for the same job. A confident DIYer with a lift and a torque wrench can do it for the price of parts, roughly $260 to $520 with fluid and filter.

Can you drive a car with a bad 722.6 conductor plate?

It will drive, but only in limp mode, usually locked in second or third with no converter lockup. Short trips to a shop are fine. Extended driving is not, because limp mode holds high line pressure and the unlocked converter dumps heat into the fluid, which cooks the clutch packs.

What are the symptoms of a failing 722.6 conductor plate?

A sudden drop into limp mode with no warning, usually at a stop or on a cold start; harsh or missing shifts; no downshift back to first; a speedometer or shift indicator that drops out; and often a red ATF puddle at the 13-pin connector on the side of the case.

Do I have to replace the TCM along with the conductor plate?

Only if fluid has already wicked up the harness and reached it. Pull the 13-pin connector and look inside the plug. Dry means the plate and sleeve alone will fix it. Oily means the module is contaminated, and both the sleeve and the module need attention, because new plates keep failing when they are wired to a corroded module.

Is the NAG1 in a Jeep or Dodge the same conductor plate as a Mercedes?

The units are the same family, so the plate looks the same and installs the same way, but calibration and part numbers differ between Mercedes and the Chrysler-badged NAG1 applications. Order by VIN or by the number stamped on the old plate, never by eye.