rescueranger

iTrader: (15)

Question, getting the CEL 13 CODE which is MAP Sensor;
does this mean the MAP sensor has gone bad? or is it indicative of some other issue related to vacuum pressure in the UIM?

Car cranks and will run for a few seconds and then stall out.
Will keep running if I give it some gas, but once I let off on the gas pedal the engine will stall out.

I've tried replacing the MAP Sensor with a used one, same issue.
Is it safe to assume the replacement sensor is bad as well?

Pete_89T2

iTrader: (4)

Either the MAP sensor is bad, or its wiring is damaged (i.e., shorts, open circuits, intermittent poor connections). You'll need the FSM wiring diagram to troubleshoot further, but the gist of it is there are 3 terminals on the MAP sensor with 3 wires connecting the MAP sensor and the ECU. One terminal/wire will be for +5VDC power, one will be the ground return, and one will be the MAP output signal. First thing to do will be to verify that each MAP sensor terminal is reading the correct voltages with the key switched on/car not running.

rescueranger

iTrader: (15)

thank you, i will test the wiring harness

j9fd3s

iTrader: (3)

if you've tried two sensors, and that didn't fix it, its probably not the sensor.

the code will set if the signal voltage is too high or too low.

rescueranger

iTrader: (15)

I bought a used sensor, so i cant really confirm if the sensor is truly without fault.

rescueranger

iTrader: (15)

I found the pin on the ecu that's connected to the MAP sensor (1O), do i just do a continuity test? to make sure the wire is not shorting out?

scotty305

iTrader: (2)

The ECU cares about the voltage at the sensor input wire. With the car off (key out of the ignition), I would check resistance between the ECU pin (1O) and the sensor connector (wire should be grey with yellow stripe for a 1994 car, according to the service manual). Your multimeter probes won't be long enough to do this check without adding an extra length of wire, and you might need something small and pointy to reach the pins inside the connector without damaging the plastic connector housing. Resistance between the ECU pin and the sensor connector should be very low, less than 10 ohms. If it's higher, that usually needs to be fixed. High resistance can be from connectors unplugged, or corroded metal pins/sockets not making a good electrical connection, or from wires that have been frayed or sliced or broken or pulled apart or burned.

If the resistance from the ECU input pin to the sensor signal pin is low, I would next check the resistance between the sensor's ground pin (center pin, black/green wire) and the ECU ground wire (pin 4D on the ECU). This should also be low, below 10 ohms. If the resistance is too high, I would double-check that connector X-05 is connected.

It's late here and this feels pretty long already, but hopefully that's enough to get you started. Good luck, sensor or wiring troubleshooting can be tricky. If it's hard to access the ECU, unplug the MAP sensor and measure voltage at each of the three MAP sensor pins. The negative (black) probe of the multimeter can go to the battery negative post for those measurements. Expected voltage is between 0.00V - 5.00V for each pin, but not all three pins should be the same. Keep careful track of the wire colors when you make those measurements, it's expected for two of the pins to measure about 5.0V with the sensor disconnected but it's important to know exactly which is which.

rescueranger

iTrader: (15)

i took the car the the local mazda dealership, they tech was saying that the wires that feed the MAP sensor, all 3 pins were reading 5V, is this indicative of a short? i apologize my electrical knowledge is not up to par.