Faulty sensors preventing startup

ANSWER : Hi there. What you received from the parts store was a code retrieval, not a diagnostic. The codes are set when a fault is detected against normal operating parameter. The computer does not know what caused the fault, only that the fault meets the criteria for this code to set. There could be a problem in the wire harness, converter, or the ECM. The code and data are needed to properly assess the direction that a diagnosis needs. I strongly suggest having a qualified technician perform an inspection to avoid replacing unnecessary parts. Your Mechanic has several available technicians that can assist you with a check engine light inspection.

ANSWER : Hi there. Sometimes the material of the contact on a sensor can produce a false reading or not correctly connect to the electrical harness; so if your trying to test the sensor to see if it works, and the OEM sensor is made of a different component or designed for a different use, it’s probably not best to try that. I’m not sure if it would negatively impact the ECU, but I have seen stranger things cause communication errors.

ANSWER : When you say you have three bad sensors I can only assume you have had them tested and the end result is three bad sensors. If they tested bad then they should be replaced. The power steering sensor senses the load of the steering on the engine so it can raise the idle during parking maneuvers. The O2 sensor is used for fuel control and it may effect engine power and fuel mileage. The camshaft sensor cay cause no starts, engine running problems and all three will turn on the check engine light.

ANSWER : Hello. Yes we will install parts that are provided by you but doing so will void our warranty. You will also be charged for the technicians time if the part you provide does not fit properly. After we install the parts if the condition returns we will come back out and inspect the vehicle. If the issue is not related to the service we performed you will be charged an inspection fee but if it is related we would turn that over to our warranty claims department. The harness is something that our parts department can obtain for you when you’re ready to schedule your next appointment. I will ask our customer service department to send you a quote for the knock sensor installation and they should be able to get a price for that harness too. Thank you for choosing YourMechanic!

ANSWER : If the check engine light is on, what kind of codes is the system detecting? Do you have spark at the plugs? If you have spark, does spritzing some starter fluid give you a momentary startup? If so, there is a fuel issue. More symptoms and information on the car’s behavior before and after the parts you replaced would be very helpful. At this point, I would recommend an inspection from YourMechanic.com to diagnose this car starting problem, get an accurate assessment of damage and cost estimate for repairs. YourMechanic.com can dispatch a mobile, professional mechanic to your location to help you get your car up and working again.

ANSWER : Depending on the vehicle and tire pressure system you can find out what sensor is defective by scanning the TPMS system to isolate the failed sensor. Another way is to use a sensor activator scanner near each wheel to test each sensor’s output.

ANSWER : Hi there. It is quite possible that your car has entered what we call a fail safe or "limp mode" due to an error code being activated and stored in the ECU. This will occur when the ECU or a sensor detects a mechanical or electrical fault on one or several fuel, ignition, cooling or powertrain systems. It’s designed to allow you to safely "limp" your car to a repair facility or home so a professional mobile mechanic can complete a car is slow to accelerate inspection and determine the right course of action. It is also possible that this issue is caused by a loose vacuum line or other component like the throttle position sensor.

ANSWER : Hi there. O2 sensor low voltage can be caused my a number of things. Mass air flow sensor was only one of them. It can be a bad O2 sensor, coolant temperature sensor, or wiring issue.

What should be done is a proper diagnosis for the Check Engine Light. Using a complete scanner rather than just a code reader gives a technician the opportunity to not only read trouble codes, but to read voltages for individual sensors. While a code reader tells you the relevant system that set the Check Engine Light on, but with a number of possible causes, the full scan tool allows checking of each individual cause. Having a proper diagnosis will help you have this repaired correctly without replacing parts that are not faulty.