Acura Rough Shift & Flashing D4 Light: MDX, TL, CL, RL & RLX

Acura Rough Shift and a Flashing D4 Light

On many Acura automatics, a transmission fault makes the D4 (or D) indicator flash, turns on the check engine light and makes the shifts harsh, late or slippy. This guide covers the MDX, TL, CL, RL and RLX, which use Honda-built automatics with the same warning system. It brings our model-by-model posts together in one place.

Check for recalls for your vehicle first; some of these transmissions had extended coverage. Every code is explained in our P0700–P0799 transmission code list.

Which Acuras This Covers

• MDX (2001–2017): the D4 light flashing with a rough 2–3 or 3–4 shift is the most common complaint; early MDX five-speed automatics are known for transmission failures.
• TL (1999–2014): the 1999–2003 TL five-speed automatic is known for this; later TLs more often show a sensor, solenoid or fluid problem first.
• CL (1997–2003): the 2001–2003 CL five-speed automatic shares the early-2000s transmission problems.
• RL (2006–2012) and RLX (2014–2017): less common, and usually a sensor, solenoid or old fluid before a mechanical failure.

Symptoms

• Rough or harsh shifting, often between 2nd and 3rd or 3rd and 4th.
• D4 or D light flashing, which may come and go.
• Check engine light on at the same time.
• Slipping or flaring: the engine revs up between gears.
• Delayed engagement when you select Drive or Reverse.

Common OBD Codes

• P0700: transmission control system malfunction (the transmission computer has stored its own code)
• P0715: input/turbine speed sensor circuit
• P0720: output speed sensor circuit
• P0730: incorrect gear ratio
• P0740: torque converter clutch circuit
• P0741: torque converter clutch performance or stuck off
• P0750: shift solenoid A
• P0780: shift malfunction
• P1768: Honda/Acura code for the clutch pressure control (linear) solenoid

Mechanical Failure or a Sensor, Solenoid or Fluid Problem?

If the transmission shifts roughly or slips all the time, worn clutch packs inside the transmission are likely. If it drives normally but the D4 light and codes keep coming back, a speed sensor, a shift or pressure control solenoid, wiring, or old, contaminated fluid is more likely. Gear ratio and torque converter codes (P0730, P0740) on a high-mileage car with dark fluid often point to internal wear. A fluid change will not repair worn parts, but on a transmission that is still healthy it can smooth the shifts and delay a failure.

DIY: Transmission Fluid Drain and Fill

You will need: jack and jack stands or ramps, a drain pan, a socket set and torque wrench, a funnel, gloves and safety glasses, and the correct fluid.

Use genuine Honda ATF (ATF DW-1, which replaced the older Z1) or the fluid your owner’s manual specifies. Universal fluids can cause shift problems in these transmissions.

1. Warm it up: drive for a few minutes, then park on level ground with the parking brake on.
2. Raise the car safely and support it on jack stands.
3. Drain: remove the transmission drain plug with the pan underneath and let the fluid drain completely. Fit a new washer on the plug and tighten it to specification.
4. Refill through the dipstick tube with the amount listed in your manual.
5. Check the level with the engine warm and running or as your manual describes, and top up without overfilling.
6. Dispose of the old fluid at a recycling depot or a shop that accepts used fluids.

A drain and fill replaces only part of the fluid, so two or three changes a few hundred kilometres apart give a fuller change. Do not pressure-flush a transmission that is already slipping.

When to Bring It In

If the D4 light and codes return after a fluid change, or the transmission slips, it needs proper diagnosis: transmission data, solenoid and sensor tests, and a look at the fluid. Radman Auto Repair at 321 Rexdale Blvd, Etobicoke, diagnoses Acura transmissions before recommending any repair. See transmission repair cost and check engine light diagnosis.

Frequently Asked Questions

Why is the D4 light flashing on my Acura?

The transmission computer has found a fault and stored a code. Flashing D4 usually comes with rough shifts and a check engine light. Read the codes to see whether it is a sensor, a solenoid, or a mechanical problem.

Can I keep driving with the D4 light flashing?

Gently and for short distances only. If the transmission is slipping, driving on it can turn a repairable problem into a failed transmission. Get the codes read soon.

Will a transmission fluid change fix a rough shift?

It can help when the fluid is old and the transmission is still healthy, especially with the correct Honda fluid. It will not fix worn clutch packs or a failed solenoid.