Mazda 3 2004 1.6i EUDM No crank, no start
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Mazda 3 2004 1.6i EUDM No crank, no start
Hey everyone.
I'm not sure if I'm posting on the right forum.
I'm having some issues.
I've replaced the timing chain on the motor since it started to rattle. ODO currently reads 160k Miles or 260k Kilometres.
The car started fine and drove well.
Since i bought it (dirt cheap), the OBD read that the knock sensor was faulty, which i replaced with a new OEM one.
The problem is at follows,
since i reassembled the intake manifold and reconnected all the vacuum lines, the car fails to crank and start. Dash works normally, no flashing immobilizer light, headlights and everyting works. The fuel pump is supplying fuel to the injectors.
OBD is throwing error code U1900 ( No communication with PCB). May i mention that i tested the fuses, relays and even cleaned the ECU with isopropyl alcohol.
Before i start tearing up everything again, does anyone have any suggestions as what would cause this issues, would hate to disassemble everything again.
Thanks for the replies, and i hope i get this sorted since i really like this car. Pulls well enough and the ride is smooth.
Thanks for any suggestions,
Matt
I'm not sure if I'm posting on the right forum.
I'm having some issues.
I've replaced the timing chain on the motor since it started to rattle. ODO currently reads 160k Miles or 260k Kilometres.
The car started fine and drove well.
Since i bought it (dirt cheap), the OBD read that the knock sensor was faulty, which i replaced with a new OEM one.
The problem is at follows,
since i reassembled the intake manifold and reconnected all the vacuum lines, the car fails to crank and start. Dash works normally, no flashing immobilizer light, headlights and everyting works. The fuel pump is supplying fuel to the injectors.
OBD is throwing error code U1900 ( No communication with PCB). May i mention that i tested the fuses, relays and even cleaned the ECU with isopropyl alcohol.
Before i start tearing up everything again, does anyone have any suggestions as what would cause this issues, would hate to disassemble everything again.
Thanks for the replies, and i hope i get this sorted since i really like this car. Pulls well enough and the ride is smooth.
Thanks for any suggestions,
Matt
Senior Member
Joined: Oct 2018
Posts: 10,665
Likes: 233
From: Northern California
Sorry to suggest but there is something you missed during your service and now you need to back track everything you did.
I hope you meticulously labeled all the parts that were disconnected and remained in the engine bay during your service?
Also, while the DTC indicated an area that may have cause the DTC it never stated it was faulty. Unless a part that comes up in a DTC is first verified to be at fault you could cause other added problem to the original unresolved ones. There is also more than just active DTC area to look at when scanning the ECU which can give clues to finding the issue. However, every time you attempt to start the engine you are adding more DTC and I/M monitors to go into alert and fault making diagnosis even more challenging.
Bottom line if the engine ran before you started the engine hard part replacement and now it's not you missed something!!!!
I hope you meticulously labeled all the parts that were disconnected and remained in the engine bay during your service?
Also, while the DTC indicated an area that may have cause the DTC it never stated it was faulty. Unless a part that comes up in a DTC is first verified to be at fault you could cause other added problem to the original unresolved ones. There is also more than just active DTC area to look at when scanning the ECU which can give clues to finding the issue. However, every time you attempt to start the engine you are adding more DTC and I/M monitors to go into alert and fault making diagnosis even more challenging.
Bottom line if the engine ran before you started the engine hard part replacement and now it's not you missed something!!!!
Thread Starter
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Junior Member
Joined: May 2025
Posts: 2
Likes: 0
Sorry to suggest but there is something you missed during your service and now you need to back track everything you did.
I hope you meticulously labeled all the parts that were disconnected and remained in the engine bay during your service?
Also, while the DTC indicated an area that may have cause the DTC it never stated it was faulty. Unless a part that comes up in a DTC is first verified to be at fault you could cause other added problem to the original unresolved ones. There is also more than just active DTC area to look at when scanning the ECU which can give clues to finding the issue. However, every time you attempt to start the engine you are adding more DTC and I/M monitors to go into alert and fault making diagnosis even more challenging.
Bottom line if the engine ran before you started the engine hard part replacement and now it's not you missed something!!!!
I hope you meticulously labeled all the parts that were disconnected and remained in the engine bay during your service?
Also, while the DTC indicated an area that may have cause the DTC it never stated it was faulty. Unless a part that comes up in a DTC is first verified to be at fault you could cause other added problem to the original unresolved ones. There is also more than just active DTC area to look at when scanning the ECU which can give clues to finding the issue. However, every time you attempt to start the engine you are adding more DTC and I/M monitors to go into alert and fault making diagnosis even more challenging.
Bottom line if the engine ran before you started the engine hard part replacement and now it's not you missed something!!!!
Indeed it was a derp on my part. There was no communication because i grounded a wire to a painted area. My bad. Thanks for the reply.
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