The PCM then sends that signal to the dash. the coolant temperature sensor signal goes directly to the PCM. If none of that is happening, then it's possible that it's because the PCM isn't doing its job.Ģ) Here's the kicker. I say this for two reasons:ġ) the PCM not only turns the fuel pump on, but it also controls all aspects of both injection and spark. Honestly, at this point, I wouldn't rule out the possibility that the PCM(ECU) is somehow dead. I just deleted a paragraph i was writing on how to go about troubleshooting that the relay is getting power, and that the fuel pump itself is good by applying power directly at the pump, but it's really impossible to walk though the needed troubleshooting in a forum post. If you get that working, and your car starts, then you're good to go!ĭo you have a factory service manual? It's got the wiring diagrams, troubleshooting steps, harness pinouts (for reference) and other good stuff like that. Why? because there aren't nearly as many factors that control whether your fuel pump turns on. Your lack of fuel pressure is your main concern. At this point, I wouldn't worry about the spark plugs just yet. try some of that and let us know what you find. The ECU should still give the OK to start with a bad temp sensor-will most likely give a check engine light, though. try unplugging the engine coolant outlet water temperature sensor (this is the one that tells the computer how hot the engine is). If the temp gauge is always at hot, even after hours of not driving, then the sensor could be bad. bad relay (try switching it out for something less useful, like the A/C relay, if they're the same) faulty wiring (shorting to ground, which would cause a blown fuse) no prime pulse signal from the ECU (could be back to the 'bad ECU' idea above) So you put the key in and turned it to "on"? Did you wait and listen for the fuel pump prime pulse before starting to crank? What have you done to determine that the fuel pump is not getting electricity? cam position sensor is bad (the sensor is on the left side of the valve cover on the 2.0L) otherwise it won't spark even if it's good. did you check more than one plug? Make sure that you hold the spark plug against the engine block or a good ground when checking. I would not just to this conclusion unless it was only 1 coil that wasn't sparking. Without looking at ECU flowcharts (you'd have to work for Mazda to get them), I don't think that the temp gauge pegged at hot would stop the car from starting. This can be one of the most frustrating problems to diagnose.
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