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2007 Mazda 6 Electrical issue

4K views 30 replies 6 participants last post by  Briand 
#1 ·
I have a 2007 Mazda 6 hatchback. I was driving it one day and it just quit running.. Now the battery drains quickly and when I turn on the key the dash lights come on and shortly after go out.

Only thing is I changed Coil Packs 5min before the car quit running.
 
#2 ·
Repair/replace the engine harness then. Youve got a short.
 
#4 ·
Well, it connects to EVERYTHING under the hood including the battery and alternator. Im not guessing here, im telling you thats the issue. They get crusty, hot, flaky, flimsy over time and many heat cycles and just fail.
 
#5 ·
Troubleshooting done.
Charged Battery Fully, Holds a charge, might have mis-stated earlier.
Pulled Fuel Pump Relay, If I jumper the HOT wire and wire that goes to Fuel pump. The Fuel Pump runs.. I never get signal to relay when key is on.
Starter works if I run a wire from small connection on Starter to Positive of battery, also receive signal to starter relay when turn key to start. Relay swapped. Looks like I have a bad wire from fuse box under hood to starter

All fuses good in both fuse boxes ( one under hood, and one in driver kick panel )
When Key in On position I get power to all fuses and relays except 'Fuel Injector fuse', 'Fuel Pump Relay'

Had the Module L38E 18 881B that is in the far left side on firewall under dash.. They checked it and said it was good.

I have tried two original keys to the car, but the 'blinking' car never goes out.. Battery on both fob's are dead, but have read that they are not needed to disable immobilizer.

Is the engine harness the two connections that are connected to 'Module L38E 18 881B' ? having no luck finding diagram.
Where is 'Immobilizer' located?

Thanks for any suggestions.
 
#6 ·
I have tried two original keys to the car, but the 'blinking' car never goes out.. Battery on both fob's are dead, but have read that they are not needed to disable immobilizer.
Thats cause its an RFID more or less.

Is the engine harness the two connections that are connected to 'Module L38E 18 881B' ? having no luck finding diagram.
I dont know, sorry, maybe @DrFeelGood can find a dia?

Where is 'Immobilizer' located?

Thanks for any suggestions.
I think in the steering column?
 
#10 ·
I just went though this same issue.
If there is no power going to the fuel pump relay, check the fuse holder. The fuse could be good but the connectors could be bad. The ECU also stopped communicating with the OBDII readers.
This was my issue, had to install an aftermarket fuse/holder for the fuel pump to avoid replacing the whole fuse box and harness.
 
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#12 ·
According to a few sites, the above module is L38E-18-881B | 2007 Mazda 6 ECU 2.3L ECM Engine Computer PCM ECU

I checked 4 wires from coil near key to that module and they were all good.. Replaced coil near Key with two others I pulled at a junk yard..

Still get the Car 'Immobilizer' light.

Would this mean bad ECM/ECU/PCM module?
 
#18 ·
I MAY have a diagram, I still have my 2007 fsm saved somewhere let me do some digging around see what I can turn up...


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#20 ·
When I went through my issue (see post #10), I also lost communication to the ECU/PCM.
On post #12 I believe you mean the coil-antenna that reads the transponder chip from the key? I read on the manual that it should not be disconnected so maybe there is a reset/program required.
Have you done a thorough check of the fuses and fuse holders?
 
#21 ·
If I jump the load side of Main relay and engage starter via a jumper wire from positive of battery. The car cranks, no start, and immobilizer light goes out....

This weekend I am replacing load wire from starter relay to starter as its bad.. Will do more troubleshooting after that..

Would be nice to have a wiring diagram, as doing troubleshooting by test light.
 
#23 · (Edited)
Would be nice to have a wiring diagram, as doing troubleshooting by test light.
Grab yourself a wiring diagram.
2007 Mazda6 and Mazdaspeed6 Original Wiring Diagram
OEM part# 999995039G07

The part you worked with just before your issue was the engine harness. It is likely that it shorted there and possibly damaged other components.
You would not be the first person this happened to. Replace the harness and go from there or take it to an automotive electrician and hope for the best.
 
#25 ·
Sorry for the delay on this, things got a little crazy during finals week at school (I'm a cybersecurity major) and I didn't have a lot of time to dig for this. Anyway this link should take yo to a folder containing basically everything I have related to my 6.
 
#28 ·
I may be off base, but I’ve had similar issues in mine. Fuel pump fuse not blown, but melted. I swapped fuses with the traction control and it fixed that bit. Later I got the immobilizer issue and that ended up being fixed by reseating the relays. No problems since. Go figure.
 
#29 ·
Mine was the MPI/EFU fuse, cost me $100 for a $.10 fuse. They felt so bad they gave me a spare fuse...
 
#30 ·
I paid $225 to my mechanic to find the issue and install a $1 fuse holder. No regrets, he had the car for almost a week (and every time I stopped by, he was at it) and the only other option would have been the scrap yard as I wasn't paying a dealer to replace the harness.
 
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#31 ·
Update Looks like Main Relay control side is not going to ground and engaging relay under hood.. If I jumper the circuit that the main relay controls I can get the car to crank. Car has to be in Neutral for it to crank. I also have no power to control side fuel pump relay under dash, yet I have power at fuse under Hood
 
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