Can a bad ignition switch be a bad PCM?
Can a bad ignition switch be a bad PCM?
If the fuses are not getting power the ignition switch may be bad. That happens some on the TJs. The gauges not responding can be an indication of a bad PCM too but without key on/start power to the PCM I would guess the problem is elsewhere.
How does the PCM work on a Ford Mustang?
There is power to the coils all the time when the key is on… sparks are made by the PCM completing the ground side of the 12v. circuit as the engine turns over… Are we on the same page yet?
How can I tell if my PCM is working?
If the fuse is good see if you are getting 12v power to the fuse which comes from the ignition switch. The same contacts probably also powers other fuses possibly including the one for the cluster which might account for the gauges not coming up that you also mentioned.
Why does my PCM not work at low volts?
Could be partial power from your gauge sweep issue too, pumps get wonky at low volts. You may not get PCM communication if the voltage to it is off as well. Need to be going after battery WAY before PCM, it being low can blow your mind with various oddball errors.
Is there a fix for coil on plug ignition?
In case you’re not familiar with this (infamous) issue, the fix is to replace all the ignition coils and the PCM, which requires reprogramming the PCM, which in turn requires two original ignition keys to reprogram/reboot the anti-theft system.
How does the PCM monitor the ignition coils?
This includes fuel injectors and ignition coils. The PCM monitors the fuel injectors by looking for open or short circuits. It monitors the ignition coils by monitoring the current in each primary circuit to see if it rises to the correct level and then falls again in response to the firing command.
Can a bad ignition switch cause a car not to start?
However, if your car has ignition switch problems, you may not be able to start the car at all. Ignition switch problems can also cause issues on the road, such as unexpected shutdowns or electrical problems.
What happens to the PCM when the ignition is turned off?
The ECM power relay, or the PCM relay, acts as a switch that provides power to the ECM. When the ignition key is turned off, the switches within the PCM relay no longer receive a battery life. If the PCM relay stops switching and working as it should, the vehicle will not function properly.
In case you’re not familiar with this (infamous) issue, the fix is to replace all the ignition coils and the PCM, which requires reprogramming the PCM, which in turn requires two original ignition keys to reprogram/reboot the anti-theft system.
What does an open circuit on a PCM relay mean?
An open circuit will result in the code P0685, which signifies a defective PCM power supply relay, a low system voltage, damaged or disconnected connectors, including battery terminals, a defective ignition switch, and a failed PCM or control module.
What causes the ignition switch to fail on a glow plug?
The relay is the main cause of failure under this code Check for power from the ignition switch to the relay with the key on Check for relay actuation by disconnecting the oil temperature sensor and turning on the key. It will click when activated. Remove the ground on the small relay terminal and jumper it to ground.
