Your vehicle has no idle sensor , it has electronic throttle control . Has 2 position sensors in the gas pedal assembly an 2 position sensors in the throttle body ,plus a DC motor that controls the idle . The sensors are inputs to the engine computer ,the computer controls the DC motor to control idle .
DTC P1121 ELECTRIC THROTTLE CONTROL ACTUATOR PFP:16119 Component Description UBS002XS Electric throttle control actuator consists of throttle control motor, throttle position sensor, etc. The throttle control motor is operated by the ECM and it opens and closes the throttle valve. The throttle position sensor detects the throttle valve position, and the opening and closing speed of the throttle valve and feeds the voltage signals to the ECM. The ECM judges the current opening angle of the throttle valve from these signals and the ECM controls the throttle control motor to make the throttle valve opening angle properly in response to driving condition. On Board Diagnosis Logic UBS002XT These self-diagnoses have the one trip detection logic. FAIL-SAFE MODE When the malfunction is detected, ECM enters fail-safe mode and the MIL lights up. DTC Confirmation Procedure UBS00CVM NOTE: ? Perform PROCEDURE FOR MALFUNCTION A AND B first. If the DTC cannot be confirmed, perform PROCEDURE FOR MALFUNCTION C. ? If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at least 10 seconds before conducting the next test. PROCEDURE FOR MALFUNCTION A AND B With CONSULT-II 1. Turn ignition switch ON and wait at least 1 second. 2. Select "DATA MONITOR" mode with CONSULT-II. 3. Shift selector lever to D position (A/T) or 1st position (M/T), and wait at least 3 seconds. 4. Shift selector lever to P position (A/T) or Neutral position (M/T). 5. Turn ignition switch OFF and wait at least 10 seconds. 6. Turn ignition switch ON and wait at least 1 second. 7. Shift selector lever to D position (A/T) or 1st position (M/T), and wait at least 3 seconds. 8. Shift selector lever to P position (A/T) or Neutral position (M/T). 9. Turn ignition switch OFF, wait at least 10 seconds, and then turn ON. 10. If DTC is detected, go to EC-357, "Diagnostic Procedure" . With GST Follow the procedure "With CONSULT-II" above. DTC No. Trouble diagnosis name DTC detecting condition Possible cause P1121 1121 Electric throttle control actuator A) Electric throttle control actuator does not function properly due to the return spring malfunction. ? Electric throttle control actuator B) Throttle valve opening angle in fail-safe mode is not in specified range. C) ECM detects the throttle valve is stuck open. Detected items Engine operating condition in fail-safe mode Malfunction A ECM controls the electric throttle actuator by regulating the throttle opening around the idle position. The engine speed will not rise more than 2,000 rpm. Malfunction B ECM controls the electric throttle control actuator by regulating the throttle opening to 20 degrees or less. Malfunction C While the vehicle is driving, it slows down gradually by fuel cut. After the vehicle stops, the engine stalls. The engine can restart in N or P position, and engine speed
SOURCE: nissan ga15 engine idle adjustment locations
The idle speed is computer controled, it is not adjustable, you most likely have sludge in the throttle valve and the idle speed control air bypass valve, clean them with carb spray with the engine running.
SOURCE: IAT Sensor Location on a 2005 Nissan Altima
It is small and round (2 wire connector) and located either in the flexiable air intake hose to the engine or in the engine air filter housing.
SOURCE: 2004 Nissan altima 2.5 liter Crankshaft Position Sensor
Yes, the sensor can be replaced in your garage (if you have some decent auto repair experience).
This is not an easy job due to the location of the crank sensor.
Below are the steps I used to replace the crankshaft position sensor.
The steps are for a 2004 Nissan Altima with a 2.5 liter engine.
Nissan has a crank and cam sensor kit. I would not buy any aftermarket sensors because of the effort required to replace the sensors. (I do not work for Nissan). The information below is compiled of tips I found on the internet and my own experience. Even though these procedures may appear lengthy, it took me much longer to figure out the correct steps involved for this task.
Even though I have included all of the steps (and hints) I used… THIS IS NOT AN EASY JOB FOR THE “DO IT YOURSELFER”
CRANK SENSOR IS LOCATED AT FIRE WALL SIDE OF BLOCK BETWEEN MOTOR MOUNT AND FLYWHEEL. YOU GET TO IT FROM TOP.
Remove the (4) allen head bolts that hold the plastic engine cover. Remove the air tube that connects the throttle chamber to air filter box. Pull off the valve cover breather hose with the air tube. Now place a drop light under the two rubber heater hoses (at the firewall on the drivers hand side), shining the light forward towards the back side of the block (below the intake runners). To see the crankshaft sensor and connector, look between the valve cover and the throttle chambers (intake runners) on the drivers side, look straight down toward the ground… look for the sensor with a black wire connector with a green tab on the side, held to the engine block with a gold colored 10mm hex headed bolt. You will need to view the sensor from this position as you are following the steps below to remove and install the crank sensor. There is a large wiring harness bracket attached to the transmission bell housing that was temporarily unbolted to aid with the removal and installation of the crank sensor.
What turned out to be the biggest problem was the connector securing the wiring harness to the sensor. Unlike the camshaft position sensor connector that is removed by squeezing in on a tab located at the top of the connector, the crank position sensor was secured to the harness via some green colored push button assembly. To remove the crank sensor connector, the green tab must depressed ALL THE WAY DOWN (towards the block) UNTIL THE GREEN TAB LOCKS INTO PLACE - REMAINING IN A “PUSHED IN” POSITION (You should hear a “click”). I was able to accomplish this by viewing the connector as described above and at the same time, reach around the back side of the engine using a 6” – 8” flat blade screw driver (with a large head) and push the green tab in towards the block until it locked into place. After the green tab was depressed and locked, (still viewing from above) I repositioned my hand holding a smaller flat blade screw driver to gently pry the connector off the sensor inserting the blade of the screw driver between the bottom of the connector and the crank sensor (a slight twist should do it). I do not recommend pulling on the connector wires or trying to pull the connector off with pliers as damage may result - because in my world of auto repair, if there is a chance that something will break because I am not careful… IT WILL BREAK! After you have removed the connector and while viewing from above, use a ¼” drive ratchet with a 6” extension and a 10mm socket to loosen the gold bolt holding the crank sensor in place. I recommend that you loosen the bolt with the socket, then reach your hand around to the connector and remove the bolt by hand. After the bolt is removed, use an 8” slip jaw pliers - set at its widest opening setting – to grab the sensor. First twist then pull out the sensor.
Be sure to clean the inside of the sensor’s wiring connector with break cleaner spray and blow out with compressed air to get rid of any oil that may have leaked into the connector from the defective crank sensor… this is what probably caused the trouble code in the first place.
You are now ready to install the new crank sensor. If you purchased the crank and cam sensor kit from Nissan, make sure that sensor with white dot at bolt whole goes to the crank. Be sure to oil the rubber “O” ring. I was not able to get the green tab on the connector to snap back into place while the new sensor was installed in the block. I installed the connector to the sensor while it was out of the block – the green tab still did not pop back into its original position on its own – so…while the connector was installed as far down as I could push it, it used a small flat blade screw driver to push on the bottom of the green tab towards the top. That did the trick. While viewing from above, I placed the crank sensor back into the block. I was not able to get the rubber “O” ring to seat within the block by hand. I used the gold bolt to draw the sensor in while slowly tightening. HINT: I taped the outside of the washer of the crank sensor bolt to the 10mm socket to hold the bolt on place while I inserted the bolt into the block… you can do this by hand, but I didn’t want to drop the bolt . I also taped the socket to the ratchet extension so the socket would not get stuck on the bolt (it’s a snug fit down there).
If you were able to accomplish the above procedures, the cam sensor is a snap to remove in install. It is located in the driver’s side portion of the head facing the wheel.
Remember to reinstall all brackets and items that were removed.
Good luck!
SOURCE: high idle stalls at lights code for crank sensor
Crankshaft and Camshaft Position Sensors
Camshaft Position Sensor
Engine timing is determined from the relationship between the crankshaft and camshaft. This relationship is maintained by a timing chain or timing belt. The Engine Management System does not control engine timing but it does monitor the relative position and speed of these shafts by monitoring signals generated by sensors. The Engine Management System (EMS) uses signals generated by the camshaft position sensor to synchronize fuel injection to the valve sequence and for the on-board diagnostic procedure for misfire detection. The EMS energizes the injector at or near the time the intake valve opens. For misfire diagnosis, the EMS compares the number of camshaft sensor reference pulses and the number of crankshaft position sensor reference pulses received. If the EMS receives an incorrect number of pulses Diagnostic Trouble Codes (DTC’s) should be stored in the EMS.
If the camshaft position sensor or circuit is faulty most engines will start. Some engine management systems will then default to a pre-programmed injector firing sequence. All injectors may be energized simultaneously or all of the injectors on one bank may be energized at the same time. If the CMP data is required for misfire detection and reliable CMP data is not present misfire detection would probably be suspended.
Related Symptoms
The following symptoms can be caused by an intermittent wiring connection or faulty signal to the EMS:
Crankshaft Position Sensor
Engine speed is a very important input to the Engine Management System (EMS). Crankshaft speed and position are the basis for many calculations made by the computer. Crankshaft position values are transmitted to the computer by pickup coils also known as Permanent Magnet (P/M) generators, hall-effect sensors or optical sensors. The Crankshaft Position Sensor (CKP) also known as engine speed sensor is located in close proximity to the crankshaft.
In addition the EMS uses minute variations in the CKP sensor data to determine engine misfire. The EMS uses this information in conjunction with the camshaft position sensor to perform misfire diagnostics.
Related Symptoms:
No Start/Intermittent Start Condition – Can be caused by a faulty crankshaft position sensor due to loose connections, bad grounds, high resistance in the circuit, or opens in the circuit
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