In most cases, a blower motor resistor fails due to corrosion or overheating. In some cars, a failed blower motor resistor can cause a heater fan to stop working completely. The most common symptom of a failed blower motor resistor is when the heater fan only runs at the highest speed setting (4 or 5) and doesn't work at low speeds. Problems with a blower motor resistor are common in many cars. Steps to diagnoseīlower motor resistor / control module problems Signs of automatic transmission problems.
#Power transistor wiring harness how to#
#Power transistor wiring harness driver#
If there is a low resistance on the wire for the #4 injector only, then the driver transistor in the PCM or the wire to it has shorted out. With power off, unplug the harness from the injector and check the resistance of the pin on the harness (not on the injector) that the ground seeking wire is attached to and a nearby ground. The hot wire should be the same color to all injectors, but the ground seeking wire should be a different color for each injector. There should only be two wires on each injector, one hot wire and one that seeks ground through the PCM. Long story short: Providing that’s the cause of your PCM dying, I’d replace the injector as well - just to make sure.
No doubt your injector has that diode across it somewhere but, if that diode goes bad, you could do damage to your new PCM as well. To circumvent it, coils should have a diode across them to short that collapsing voltage. It may not damage them immediately, but all this zapping will age them prematurely. That reverse voltage could potentially zap the driving electronics. It wants to retain that charge and as the field collapses, it generates a fairly large very fast pulse of the opposite polarity (a phenomena called “Back EMF”).ĭepending on the coil, that voltage could be several hundred volts but just a couple of microseconds in duration. If you see a solid ground connection there at all times, that PCM may have an issue.Īn injector is a coil, from an electrical point of view.Ī coil that has a voltage applied to it and then when you turn it off, it fights to sustain its electric field. On that connection, you should see rapid pulses when the car runs and nothing when the car is not running. I’d try to make sure that wire to the injector has absolutely no short to anything else. It sounds like the PCM has a short to ground on that driver or, inside the PCM, whatever drives that driver is active all the time. It turns the pump on but it is not supposed to open the injectors to spray inside the cylinder. That spraying for four seconds is part of the system priming. So - just to clarify - that injector stops spraying when you turn the key off, sprays for four seconds when you turn the ignition on and sprays all the time (no pulses) when the engine is running? I don’t think people will email you because we’d all be duplicating effort and it will not help people that may have this problem in the future.
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