My maf shows low voltage. How can I solve this issue

Could be a problem with the wiring harness, or a major leak in the air intake system, or a blockage.
The low voltage would happen if the sensor is not detecting air flow thru it from the air filter to the intake.

the FSM covers this,
It measures, air flow. from idle , to wide open throttle.
There are only 2 ways to test it.
1 is with a scan tool. ill skip this test as you prob. dont have one.
2: check the voltage at the output pin.
key on about 1v
idle, about 2v
and full throttle rises to 3v, or more , can go to above 4v under full load (full horse power going up tall hill, wideopen throttle)
it measures AIR MASS.
the tests are here. for $4 you too can read them, under engine electronic controls
https://suzukipitstopplus.com/category/3-suzuki-service-manuals.aspx
102 (that is P0102)
Mass Air Flow (MAF) Sensor Circuit Low Voltage
this means
1: no power to MAF,
2: no ground to MAF.
3: the output pin at MAF is cut and is open
4: bad maf.

Don't even THINK about replacing the PCM right now. That's way down the list of possibles.The P0102 can be caused by a significant vacuum leak and that would also cause a very high idle speed. Check the air duct that runs from the MAF to the intake. Look for anything that would let in unmetered air. The P0122 is pretty easy to check. Remove the plug from the TPS and measure reference voltage (key in RUN position) on the gray wire. It should be 5V dc. If it's not, backprobe the gray wire right at the PCM at pin 16. You should see 5-volts there. If you do, then you have a wiring issue between the PCM and TPS. The reference voltage is spliced between the PCM and the TPS. The splice provides the 5v to the linear EGR vavle, MAP and fuel tank pressure sensor.

Until you check the reference voltage, you have NO basis to think that the problem is in the PCM.

They share the engine wiring harness from the computer (called the PCM) and a common ground circuit, which is referred to as the signal return. So I think you need to look for a defective ground.

P0113 Intake Air Temperature (IAT) Circuit High Input Indicates the sensor signal is greater than Self-Test maximum. The IAT sensor maximum is 4.6 volts or -50 C (-58 F). Possible causes are Open circuit in harness, Sensor signal short to power, Damaged Sensor, Improper harness connection, Damaged PCM

P0102 Mas Air Flow (MAF) Circuit Low Input, The MAF sensor circuit is monitored by the PCM for low air flow (or voltage) input through the comprehensive component monitor (CCM) If during key ON engine running the air flow (or voltage) changes below a minimum calibrated limit, the test fails. Possible causes are MAF sensor disconnected, MAF circuit open to PCM, VPWRopen to MAFsensor, PWR GND open to MAF sensor, MAF RTN cirbuit open to PCM, MAF circuit shorted to GND, Intake air leak (near MAF sensor), A closed throttle indication, Damaged MAF sensor, Damaged PCM.

grey/red signal return
Red Power
Black/*********** ground
Tan/Light blue MAF signal return
Light blue/Red Maf signal
Grey intake air temp

To retrieve OBDII Error codes from your Chrysler/Jeep/Dodge vehicle, do the following sequence with the key: ON-ACC-ON-ACC-ON and look at the odometer, that is where codes will be displayed. Here are the codes that you may/can get.

Ho2S = heated oxyen sensor, TP = throttle position, MAF = mass airflow, MAP = manifold absolute pressure, TC=turbocharger.P0030 HO2S Heater Control Circuit Bank 1 Sensor 1
P0031 HO2S Heater Circuit Low Voltage Bank 1 Sensor 1
P0032 HO2S Heater Circuit High Voltage Bank 1 Sensor 1
P0036 HO2S Heater Control Circuit Bank 1 Sensor 2
P0037 HO2S Heater Circuit Low Voltage Bank 1 Sensor 2
P0038 HO2S Heater Circuit High Voltage Bank 1 Sensor 2
P0050 HO2S Heater Circuit Bank 2 Sensor 1
P0051 HO2S Heater Circuit Low Voltage Bank 2 Sensor 1
P0052 HO2S Heater Circuit High Voltage Bank 2 Sensor 1
P0056 HO2S Heater Circuit Bank 2 Sensor 2
P0057 HO2S Heater Circuit Low Voltage Bank 2 Sensor 2
P0058 HO2S Heater Circuit High Voltage Bank 2 Sensor 2
P0100 MAF Sensor Ckt. Insufficient Activity
P0101 Mass Air Flow (MAF) Sensor Performance
P0102 Mass Air Flow (MAF) Sensor Circuit Low Frequency
P0103 Mass Air Flow (MAF) Sensor Circuit High Frequency
P0104 Mass Air Flow Circuit Intermittent
P0105 MAP Sensor Circuit Insufficient Activity
P0106 Manifold Absolute Pressure (MAP) System Performance
P0107 Manifold Absolute Pressure (MAP) Sensor Circuit Low Voltage
P0108 Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage
P0109 Manifold Absolute Pressure Circuit Intermittent
P0110 Intake Air Temperature (IAT) Sensor Circuit
P0111 Intake Air Temperature (IAT) Sensor Performance
P0112 Intake Air Temperature (IAT) Sensor Circuit Low Voltage
P0113 Intake Air Temperature (IAT) Sensor Circuit High Voltage
P0114 Intake Air Temperature Circuit Intermittent
P0115 Engine Coolant Temperature (ECT) Sensor Circuit
P0116 Engine Coolant Temperature (ECT) Sensor Performance
P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage
P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage
P0119 Engine Coolant Temperature Circuit Intermittent
P0120 Throttle Position System Performance
P0121 Throttle Position Sensor Circuit Insufficient Activity
P0122 Throttle Position (TP) Sensor Circuit Low Voltage
P0123 Throttle Position (TP) Sensor Circuit High Voltage
P0124 Throttle Position Sensor 1 Circuit Intermittent
P0125 Engine Coolant Temperature (ECT) Insufficient for Closed Loop Fuel Control
P0126 Insufficient Engine Coolant Temperature for Stable Operation
P0128 Coolant Thermostat
P0130 HO2S Circuit Closed Loop (CL) Performance Bank 1 Sensor 1
P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1
P0132 HO2S Circuit High Voltage Bank 1 Sensor 1
P0133 HO2S Slow Response Bank 1 Sensor 1
P0134 HO2S Circuit Insufficient Activity Bank 1 Sensor 1
P0135 HO2S Heater Performance Bank 1 Sensor 1
P0136 HO2S Circuit Bank 1 Sensor 2
P0137 HO2S Circuit Low Voltage Bank 1 Sensor 2
P0138 HO2S Circuit High Voltage Bank 1 Sensor 2
P0139 HO2S Slow Response Bank 1 Sensor 2
P0140 HO2S Circuit Insufficient Activity Bank 1 Sensor 2
P0141 HO2S Heater Performance Bank 1 Sensor 2
P0142 HO2S Circuit Bank 1 Sensor 3
P0143 HO2S Circuit Low Voltage Bank 1 Sensor 3
P0144 HO2S Circuit High Voltage Bank 1 Sensor 3
P0145 HO2S Circuit Bank 1 Sensor 2 Slow Response
P0146 HO2S Circuit Insufficient Activity Bank 1 Sensor 3
P0147 HO2S Heater Performance Bank 1 Sensor 3
P0150 HO2S Circuit Closed Loop (CL) Performance Bank 2 Sensor 1
P0150 HO2S Circuit Bank 2 Sensor 1
P0151 HO2S Circuit Low Voltage Bank 2 Sensor 1
P0152 HO2S Circuit High Voltage Bank 2 Sensor 1
P0153 HO2S Slow Response Bank 2 Sensor 1
P0154 HO2S Circuit Insufficient Activity Bank 2 Sensor 1
P0155 HO2S Heater Performance Bank 2 Sensor 1
P0156 HO2S Circuit Bank 2 Sensor 2
P0157 HO2S Circuit Low Voltage Bank 2 Sensor 2
P0158 HO2S Circuit High Voltage Bank 2 Sensor 2
P0159 HO2S Slow Response Bank 2 Sensor 2
P0160 HO2S Circuit Insufficient Activity Bank 2 Sensor 2
P0161 HO2S Heater Performance Bank 2 Sensor 2
P0162 HO2S Circuit Bank 2 Sensor 3
P0163 HO2S Circuit Bank 2 Sensor 3 Low Voltage
P0164 HO2S Circuit Bank 2 Sensor 3 High Voltage


P

These trucks have what is called a smart charge system. It normal for the alternator light to elluminate when the truck requires no charging or the idle is low. The most likely reason you have low idle is throtttle body coking which requires cleaning or a bad idle air control valve. Also clogged injectors will cause a low rough idle but if that was the case misfires would show up and can be seen while they happen using a diagnostic data scanner.
And the first thing we always look at is the air cleaner. If you have a K/N filter the oil can contaminate the MAF senor. If the sensor cannot see and feel the air then it won't be able to add fuel causing a low idle, The MAF can be sprayed with brake cleaner to clean it. Usually you will get a p0171 and or a p0174 if the maf was causing a lean condition.

1. At the Mass Air Flow (MAF) sensor connector, backprobe the Gray (GY) wire at terminal #6 with the key on and the MAF sensor connected. Typical voltage will be about 2-3.5v depending on temperature.

2. If the voltage is above 4.5v (which is what the code P0113 indicates) check the voltage on the Gray/Red (GY/RD) wire at terminal #1 of the MAF sensor connector. The voltage on the GY/RD should be less than about 0.1v.

3. If the GY/RD wire shows less than 0.1v and the voltage on the GY wire is above 4.5v, inspect the connections at the MAF sensor connector. If OK, replace the MAF sensor for the open Intake Air Temperature (IAT) Sensor.

4. If the voltage on the GY/RD wire shows above 0.1v, locate and repair the high resistance between the MAF sensor and pin #91 of the Powertrain Control Module (PCM) connector.

5. If the voltage on the GY wire is not above 4.5v but the scanner shows -40 F on the data stream, check the voltage at pin 39 of the PCM. If the voltage at the PCM is above 4.5v, locate and repair the high resistance or open circuit in the GY wire between the PCM and MAF sensor connector

poor start, very poor gas millage