Damaged, corroded or loose wiring or connectors between the PCM and the TCS/ABS/DSC module; Low battery voltage or poor power and earth supply to the PCM or TCS module; Faulty TCS, ABS or DSC control module; Water ingress or corrosion in a connector or module housing; Faulty PCM or internal communication circuit fault; Outdated PCM or TCS module software where a known fault is documented for the model; Faulty aftermarket electrical accessory interfering with the communication line.

P1628

Powertrain Control Module ECM TCS Any Line Communication Error.

Mazda
Powertrain
Manufacturer code
Medium severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
6: AreaComputer and output circuits
28: FaultThe specific fault in that area

What it means

On Mazda, P1628 means the powertrain control module has detected a communication error on one of the lines linking it to the traction control system (TCS) module. The PCM expects regular data from the TCS or ABS/DSC unit, and the fault sets when that data is missing, corrupt or inconsistent. The exact line and set criteria vary by model and year, so check the factory information for the vehicle in front of you.

Symptoms

Engine management light on
Traction control or stability control warning light on
ABS warning light may be on at the same time
Traction control not working or intervening wrongly
Possible reduced engine power or rough running on some models
Other communication or U-codes stored alongside

Possible causes

Damaged, corroded or loose wiring or connectors between the PCM and the TCS/ABS/DSC modulelikely
Low battery voltage or poor power and earth supply to the PCM or TCS modulelikely
Faulty TCS, ABS or DSC control modulepossible
Water ingress or corrosion in a connector or module housingpossible
Faulty PCM or internal communication circuit faultpossible
Outdated PCM or TCS module software where a known fault is documented for the modelrare
Faulty aftermarket electrical accessory interfering with the communication linerare

How to diagnose

Read all stored and pending codes and freeze frame data, noting any ABS, DSC or U-codes, then record them before clearing anything
Check battery condition and charging voltage, as low voltage commonly causes communication faults
Visually inspect the wiring and connectors at the PCM and the TCS/ABS/DSC module for damage, corrosion, water and pushed-out pins
Check the relevant fuses and the power and earth supplies to both modules against the wiring diagram
Check the communication line for continuity, short to earth, short to voltage and resistance between the modules, using the model's wiring diagram
Check live data to see whether the TCS or ABS module communicates and whether wheel speed data is present
Look for any technical service bulletins or software updates for the model and engine
Clear the code, road test and recheck to see whether it returns, which helps separate a permanent fault from an intermittent one

How to fix

Repair or replace damaged wiring and clean or renew corroded connectors
Restore proper battery condition and repair any charging, power or earth supply fault
Replace the TCS, ABS or DSC module if it is confirmed faulty, with coding or setup as the manufacturer requires
Replace or repair the PCM only after wiring and the other module are proven good
Update PCM or TCS module software if a documented update covers this fault

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but traction and stability control and possibly ABS may not work, so take extra care, especially in wet or slippery conditions. Have it diagnosed soon, and stop driving if power is reduced or the car runs poorly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.