Q: What are the check procedures for the Manifold Absolute Pressure (MAP) sensor and solenoid valve on Nissan Xterra?A: The tests associated with Manifold Absolute Pressure (MAP) sensor and solenoid valve checks are specific to four cylinder and 3.3L V6 models only as the 3.5L V6 models require a scan tool for testing the absolute pressure sensor. To start the checks, remove the vacuum hose from the MAP sensor and fix a vacuum gauge, then start the engine and allow it run idle for about five seconds to confirm if there is a vacuum; lack of vacuum means that there may be cracks or blockages in the hose which connects to solenoid valves before this step is taken. If vacuum is present, proceed to evaluate of MAP sensor. Unplug electrical connector from MAP sensor. While ignition key on but engine off, measure voltage between reference wire terminal (+) and ground wire terminal (-) using a voltmeter and expect around 5 volts as approximation; otherwise look at circuits from connector to PCM for any observed defects and ask for PCM diagnosis by qualified repairer where needful. Then reconnect electrical connector back onto MAP sensor, backprobe on signal wire terminal using an appropriate probe, connect voltmeter across it with positive lead connected to probe while negative lead connected to appropriate engine ground point such that with ignition key on but engine off, meter reads approximately 2.2 to 4.8 volts. As regards checking solenoid valve, disconnect vacuum source hose from solenoid valve connect vacuum gauge, start engine looking out for intake manifold vacuum lack; failure to detect creates need to visually examine source hose for its physical problems as indicated by lack of vacuum readings on device connected between them. With confirming presence of vacuum power off vehicle and reconnecting it's hose to solenoid valve then check behavior of intake manifold vacuum during engine starting sequence there should be an initial absence of vacuum followed by its presence afterwards. If solenoid valve does not work as described above, go ahead to test solenoid valve accordingly. Disconnect electrical connector from solenoid valve and check for battery voltage between two terminals of the harness connector using the ignition key on but engine off; this will help in identifying any voltage that is not present by checking wiring harness for open circuits or damage from fuse block to the connector. In case battery voltage exists, replace the solenoids and perform off-vehicle testing, simply connect it to 12-volt battery source (positive) and ground (negative) using fused jumper wires, noting the solenoid's popping sound as voltage is applied and its corresponding air flow between ports. If any of these criteria are not met by solenoid valves they have to be replaced. To proceed with installation, first remove negative terminal of battery then disconnect electrical connector from MAP sensor or/and solenoid valve. Later on take out screws which mount MAP sensor (if equipped) or/and solenoid valve(s), detach vacuum hose(s), then remove sensor(s) or/and valve(s). Its reinstallation can be done reverse order as when deinstalled.