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Mazda CX-9 Engine Control Module

The Electronic Control Module (ECM) for the TB-series Mazda CX-9 (2007-2016) controls the running of the 3.5 and 3.7-litre V6 petrol engines found under the bonnet of this popular seven-seat SUV.

The CX-9 is a generally very reliable vehicle, but can experience issues when worn or faulty coil packs result in damage to the ECM, which may in turn present as the engine misfiring, premature ignition coil failure, or a failure to start.


Before any diagnosis, ensure battery voltage is stable and whenever possible use a battery support unit in diagnostic mode.

A visual check of all connections to the ECM, and coil packs is important, confirm they are secure and that all wiring is in good condition.

Utilize your scan tool, it may identify the coil pack with the fault, otherwise an oscilloscope setup to test the ignition circuit will help you confirm each coil pack is working.  Once you identify the faulty coil pack, replace with a working unit, if however, at this point the engine misfire fault remains, and you have any of the following DTC codes present, it typically will indicate the ECM needs to be tested and repaired.

  • P0300 – Engine misfire detected
  • P0351 – Ignition coil A primary/secondary circuit fault
  • P0352 - Ignition coil B primary/secondary circuit fault
  • P0353 - Ignition coil C primary/secondary circuit fault
  • P0354 - Ignition coil D primary/secondary circuit fault

Injectronics offer a prompt test and repair service for a variety of BCMs, ECMs, and TCMs, as well as many other automotive electronics and mechatronics.

Our CX-9 ECM test and repair process uses the customer’s own unit, checking first for any obvious visual signs of failure, then bench testing the unit to determine the fault. Once the fault is identified and rectified the unit is tested and resealed before being returned to the customer.

The ECM will retain it’s original vehicle programming data, and will be a direct plug in once returned.

In the event the ECM is beyond repair, Injectronics can source another unit which is reprogrammed to match the original. In either instance, the unit is warranted for 12 months from the time of repair.


Check out the Youtube link to the Tech Talk  or see the link to the repair part number here ECMCX9REP

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