P0740 Torque converter clutch control circuit fault

Torque converter clutch circuit

P0740 in short

P0740 means the transmission computer found a problem controlling the torque converter clutch, the lock-up that links engine and transmission at cruising speed. Wiring, connectors and the lock-up solenoid are common causes, and Honda warns against replacing the solenoid too quickly. Have it inspected soon.

At steady speed the torque converter clutch locks the engine to the transmission so the converter stops slipping, which saves fuel. A solenoid controlled by the transmission computer applies it. P0740 sets when the computer sees a fault in that control, such as an open or shorted circuit or lock-up that does not respond as commanded.

Causes vary by maker. Ford traced it on some 2017 Explorers and Tauruses to a terminal in one connector, Honda warns technicians not to replace the solenoid by default on 1999–2004 Odysseys, and Chrysler and Nissan have issued bulletins for intermittent P0740 on older models.

Most drivers notice little beyond the check engine light and perhaps slightly worse fuel economy or a higher engine speed on the highway. Have it diagnosed before a small wiring fault becomes a bigger repair.

Most likely causes

  1. Lock-up solenoid wiring or connector fault

    Common general cause
    Why it ranks here
    P0740 is a circuit-level fault on a monitored output, and Ford traced it on some 2017 models to one connector terminal.
    What would change this
    Rises if the connector shows poor terminal fit, push-out or damage.

  2. Faulty or contaminated lock-up solenoid

    Possible — needs testing
    Why it ranks here
    The solenoid is the part being controlled, but Honda warns technicians not to replace it by default for P0740.
    What would change this
    Rises if the solenoid fails a resistance or command test after wiring is ruled out.

  3. Lock-up control system fault beyond the solenoid (Honda)

    Supported by vehicle data
    Why it ranks here
    Honda Service News items give repair tips for P0740 on several 1996–2004 models and point beyond the solenoid itself.
    What would change this
    Rises on an older Honda Accord, Civic, Odyssey or Prelude, or after the transmission has been removed and refitted.

  4. Computer software (2007–2008 Chrysler, Dodge, Jeep)

    Supported by vehicle data
    Why it ranks here
    Chrysler issued a flash for P0740 or P1798 with shift improvements on many 2007–2008 models.
    What would change this
    Rises on a covered vehicle that has not had the flash.
    How to test the transmission control module (tcm)

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read codes from the engine and transmission modules with a scan tool that supports both, before anything is cleared.

    Low riskTool: scan tool that reads the transmission module

  2. Check for a P0740 bulletin for your VIN at a dealer or on the NHTSA site.

    Low risk

  3. Have a shop check the lock-up solenoid circuit and command the solenoid with a scan tool.

    Best left to a shopTool: scan tool with transmission output controls

    Warning:Shop test. It needs the maker's wiring diagram and test procedure.

Symptoms

  • Check engine light, often with no other symptom
  • Engine speed stays higher at highway cruise because the converter does not lock up
  • Transmission indicator flashing "D" on some Hondas Gets more serious: stop and have it checked.
  • Transmission stuck in one gear (limp-home mode) Gets more serious: stop and have it checked.

How to fix

  1. Do not clear the code before the transmission module has been read.

  2. Ask a dealer whether your VIN has an open P0740 bulletin. Ford, Honda, Nissan and Chrysler have issued them.

Parts and cost context

  • Transmission control module (TCM):Do not replace the transmission computer or the lock-up solenoid for P0740 until the wiring and connectors are checked. Honda specifically warns against replacing the solenoid by default.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Honda

  • 1999–2004 · Odyssey

    Supported by vehicle data

    Honda Service News warns technicians not to replace the solenoid by default when troubleshooting P0740 on the lock-up control system. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.

  • 1998–2000 · Civic

    Supported by vehicle data

    Honda Service News covers P0740 appearing after the automatic transmission has been removed and refitted. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.

  • 05012004Status unverified

    Do not replace the solenoid when troubleshooting P0740

    1999–2004odyssey · issued · NHTSA 10013990

    Service News item on P0740 (lock-up control system) on the Odyssey. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • 11012003Status unverified

    P0740 and P0741 repair tips

    1996–2001accord, odyssey, prelude, civic · issued · NHTSA 10009279

    Service News repair tips for lock-up codes on several models. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • 04012004Status unverified

    P0740 after automatic transmission removal and installation

    1998–2000civic · issued · NHTSA 10009028

    Service News item on P0740 appearing after the transmission has been removed and refitted. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Ford

  • 2017 · Explorer · 3.5L, 3.7L

    Supported by vehicle data

    Ford SSM 46719 says to check pin 14 in connector C168 first for P0740 or P0743 on vehicles built 14 to 21 June 2017. The Taurus is also covered. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.

  • SSM 46719Status unverified

    MIL with P0740 or P0743

    2017explorer, taurus · 3.5L, 3.7L · issued · NHTSA 10115959

    On vehicles built 14 to 21 June 2017, check pin 14 in connector C168 for fit, tension, push-out or damage before replacing parts. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Nissan

  • 2000–2001 · Altima

    Supported by vehicle data

    Nissan NTB01-035 covers intermittent P0740 from the torque converter clutch solenoid valve. The 2001 Quest is also covered. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.

  • NTB01-035Status unverified

    MIL on with intermittent P0740 (TCC solenoid valve)

    2000–2001altima, quest · issued · NHTSA 625185

    Covers intermittent P0740 on the 2000–2001 Altima and 2001 Quest. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • P0700Transmission module requests the check engine light

    Primary / secondary Possible — needs testing

    Likely primary: P0740. On cars with a separate transmission module, a basic code reader may show only P0700, which means the module has stored its own code. P0740 can be that code, so fix P0740 and P0700 goes with it.

  • P0741Torque converter clutch not engaging as commanded

    Same system Possible — needs testing

    P0741 means the same lock-up clutch is not engaging as commanded, a performance fault rather than a circuit fault. Honda covers both in the same repair tips.

  • P0744Torque converter clutch control signal dropping in and out

    Same system Possible — needs testing

    P0744 is an intermittent fault in the same lock-up control circuit.

All Transmission codes

P0740 questions

What is the difference between P0740 and P0741?

P0740 points at the lock-up control circuit, such as wiring, connectors or the solenoid. P0741 means the lock-up clutch is not engaging or holding even though it is being commanded.

Should I replace the lock-up solenoid?

Not before the wiring is checked. Honda warns against replacing the solenoid by default for P0740, and Ford found a connector terminal at fault on some vehicles.

Sources and review

  1. Toyota Camry Owner's Manual (OM06291U) — Toyota
  2. Cal. Code Regs. Tit. 13, § 1968.2 — Malfunction and Diagnostic System Requirements (OBD II) — California Air Resources Board (via Cornell LII)
  3. Honda owner's manual: Continuously Variable Transmission, shift lever position indicator (p. 166) — American Honda Motor Co. ,
  4. Ford SSM 46719: 2017 Explorer/Taurus MIL with P0740 or P0743 — Ford Motor Company / NHTSA ,
  5. Honda Service News (May 2004 item 05012004): do not replace the solenoid for P0740 — American Honda / NHTSA ,
  6. Honda Service News 11012003: P0740 and P0741 repair tips — American Honda / NHTSA ,
  7. Honda Service News 04012004: P0740 after transmission removal and installation — American Honda / NHTSA ,
  8. Chrysler 21-018-08: flash for P0740 or P1798 and shift improvements — Chrysler LLC / NHTSA ,
  9. DTC P0700 — Saab 9-5 (9650) 2010 Workshop Information System — SaabWISOnline (community rehost of Saab/GM service information)
  10. Nissan NTB01-035: MIL on with intermittent P0740 (TCC solenoid valve) — Nissan North America / NHTSA ,
Last reviewed
Written by
Saurabh K.
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