P1626 — Control Module Long Term Memory Performance/ Immobilizer Code Words Do Not Match

OBD2 code P1626 flags a problem with the sensor and actuator circuits (control module long term memory performance/ immobilizer code words do not match). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, blown fuse feeding the circuit, control module driver fault.

For Ford vehicles

A/C circuit open or power b+ VLCM

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P1626 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the control module long term memory performance/ immobilizer code words do not match for damage, corrosion, chafing or poor contact.
Subsystem check Measure reference voltage, ground and signal continuity at the component connector.
Subsystem check Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P1626 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P1626 (parts and labor, USD, independent shop rates): Repair wiring or connectors: $80–$250; Control module repair: $300–$1,000; Replace the faulty sensor or actuator: $150–$500. Overall, fixing P1626 usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

Is it safe to drive with P1626?

In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How much does it cost to fix P1626?

Repair wiring or connectors — $80–$250; Control module repair — $300–$1,000; Replace the faulty sensor or actuator — $150–$500. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Will P1626 clear itself?

Sometimes P1626 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What does OBD2 code P1626 mean?

How do I diagnose P1626 myself?

Start with a scan: confirm P1626, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the sensor and actuator circuits, and verify the suspect component against live data before buying parts.

When your scan tool pulls code P1626, it's telling you that the engine or transmission control unit has detected a mismatch in its permanent memory — essentially, the stored calibration data doesn't match what the module expects to see. This falls under the powertrain fault category in the OBD2 standard, and it affects how the computer manages sensors and actuators that rely on that memory information.

The control module constantly compares real-time sensor and actuator readings against values it has stored in its keep-alive memory. When those values drift outside acceptable limits over multiple drive cycles, the module logs P1626. The stored freeze frame data captures exactly what the engine was doing at the moment the fault occurred — engine speed, calculated load, coolant temperature, and vehicle speed. Technicians examine that snapshot first because it points directly toward which circuit is actually at fault, rather than chasing unrelated systems.

P1626 can stem from several different sources, ranging from simple wiring issues to a failing control module itself. The key to an accurate repair is starting with the least expensive possibilities before moving to pricier component replacements.

Common symptoms of P1626

The Check Engine light will illuminate when P1626 is active, and it typically stays on until the fault is cleared. The affected circuit may operate intermittently or fail to function altogether, depending on which sensor or actuator is involved. Some vehicles experience higher fuel consumption because the engine runs in an altered state when the module can't properly interpret sensor data. Depending on the specific system affected, the car may enter limp mode — a reduced-power state designed to protect the engine and transmission. In rare cases, related systems like traction control or certain safety features tied to the affected module may behave abnormally. The severity of symptoms varies significantly between makes and models.

What causes P1626?

The most frequent culprits are wiring and connector problems in the affected circuit — corroded terminals, loose plugs, or damaged insulation that causes intermittent shorts. A poor ground connection at the module or component can also trigger P1626 by preventing proper signal reference. An open or shorted wire in the circuit interrupts communication between the sensor, actuator, and control module. A blown fuse that feeds power to the circuit will obviously prevent proper operation and trigger this code. A faulty sensor or actuator that feeds bad data back to the module can cause the memory mismatch flag. Finally, the control module itself may have an internal driver failure that prevents it from properly reading or writing to its keep-alive memory.

How to diagnose P1626

First, connect your OBD2 scanner and confirm P1626 is stored in permanent memory — note whether it's a pending code or a confirmed failure. Save the freeze frame data before clearing anything, because it shows engine conditions like RPM, load, and temperature when the fault happened. Second, check for any related diagnostic trouble codes in the same family, as they often point to the actual root cause. Also look up technical service bulletins for your specific make, model, and year — manufacturers sometimes publish software updates or known fixes for specific P1626 issues. Third, perform a thorough visual inspection of the wiring harness and connectors associated with the affected circuit, looking for chafed wires, water intrusion, corrosion, or terminals that aren't fully seated. Fourth, use a multimeter to check reference voltage, ground integrity, and signal continuity at the component connector with the key on and engine off. Fifth, conduct a wiggle test on the harness while monitoring live data — any signal dropouts indicate a broken wire or poor connection that needs repair. Sixth, after any repairs are made, clear the code, complete a full drive cycle that reproduces the freeze frame conditions, and verify that P1626 does not return.

Repair options for P1626

The most cost-effective approach is addressing wiring and connector issues first. Damaged wires can often be spliced or terminals cleaned and re-pinned for $80 to $250 including labor. If the control module itself has failed, repair or replacement typically runs $300 to $1,000 depending on whether the unit can be rebuilt or must be sourced new and programmed. Replacing a faulty sensor or actuator in the affected circuit generally costs between $150 and $500 for parts and installation.

Total cost to fix P1626

Depending on which component is actually at fault, P1626 repairs typically range from $80 to $1,000 total. The wide range reflects how much repair costs vary between a simple wire splice and full module replacement. Getting an accurate diagnosis before purchasing parts is the best way to avoid overspending — the most expensive scenario is rarely the first thing to check.

Can you drive with P1626?

In most vehicles, the car remains driveable when P1626 is stored, though you may notice reduced performance, higher fuel consumption, or certain auxiliary features disabled. However, if the associated symptoms include stalling, failure to start, or warnings affecting brakes and steering, treat the issue as urgent and have it diagnosed immediately. Otherwise, scheduling repair within a reasonable timeframe is acceptable.