This procedure covers the removal and replacement of the alternator on a 2016-2021 Honda Civic equipped with the 1.5L turbocharged engine.

Warnings

Tools required

Parts

• Alternator × 1 — 31100-5AA-A02 or equivalent 12V 160A unit
• Serpentine belt (if damaged or worn) × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine to cool completely
3. Open hood and secure with prop rod
4. Locate alternator on passenger side of engine bay, below intake manifold
5. Take photo of serpentine belt routing for reference

Procedure

1. 1

   Disconnect battery
   Using a 10mm socket, loosen and remove the negative battery terminal bolt. Remove the negative cable and secure it away from the battery post. Wait at least 3 minutes before proceeding.
   Torque spec

   Battery Terminal Bolts8 Nm (6 lb-ft)
2. 2

   Remove engine cover
   Pull upward on the engine cover to release the mounting grommets. Set the cover aside to access the serpentine belt and upper engine components.
3. 3

   Remove serpentine belt
   Using a 3/8 inch breaker bar or serpentine belt tool, insert it into the square hole on the belt tensioner. Rotate the tensioner clockwise to release tension and slide the belt off the alternator pulley. Slowly release tensioner pressure, then route the belt off the remaining pulleys. Inspect belt for wear, cracks, or glazing and replace if necessary.
4. 4

   Disconnect alternator electrical connections
   Locate the rubber boot covering the B+ terminal on the back of the alternator. Pull back the boot and using a 10mm socket, remove the nut securing the battery cable to the B+ terminal. Remove the cable and position it aside. Depress the locking tab on the alternator connector plug and disconnect it from the alternator.
   ℹ️Do not allow the battery cable to contact ground while disconnected
5. 5

   Remove alternator mounting bolts
   Using a 14mm socket with extension, remove the upper alternator mounting bolt (near the front of the alternator). Next, remove the lower pivot bolt using a 17mm socket. Access to the lower bolt may require working from underneath the vehicle or through the wheel well.
   Torque spec

   Alternator Mounting Bolts50 Nm (37 lb-ft)

   Alternator Pivot Bolt25 Nm (18 lb-ft)
6. 6

   Remove alternator
   Support the alternator with one hand while removing the final fasteners. Carefully maneuver the alternator out of its mounting position, tilting and rotating as needed to clear the engine bay components. The alternator typically comes out toward the passenger side and upward.
   ⚠The alternator is heavy and awkwardly shaped - maintain firm grip during removal
7. 7

   Inspect mounting surfaces and hardware
   Clean the alternator mounting bracket with a wire brush to remove any corrosion or debris. Inspect the mounting bolts for damage or excessive corrosion and replace if necessary. Check that the belt tensioner operates smoothly without binding.
8. 8

   Install new alternator
   Position the new alternator into the mounting bracket, aligning the mounting holes. Insert the lower pivot bolt by hand first to hold the alternator in position, then install the upper mounting bolt by hand. Do not fully tighten bolts at this stage.
9. 9

   Torque alternator mounting bolts
   Using a torque wrench, tighten the upper alternator mounting bolt to 50.0 Nm (37.0 lb-ft). Then torque the lower pivot bolt to 25.0 Nm (18.0 lb-ft). Verify alternator is secure and does not move in its mounting bracket.
   Torque spec

   Alternator Mounting Bolts50 Nm (37 lb-ft)

   Alternator Pivot Bolt25 Nm (18 lb-ft)
10. 10

    Reconnect electrical connections
    Reconnect the alternator connector plug to the alternator until it clicks into place. Install the battery cable to the B+ terminal stud and install the retaining nut. Torque the battery cable nut to 13.0 Nm (10.0 lb-ft) using a torque wrench. Replace the rubber boot over the B+ terminal.
11. 11

    Install serpentine belt
    Following the belt routing diagram (from photo or under-hood label), route the serpentine belt around all pulleys except the alternator. Using the belt tool, rotate the tensioner clockwise and slide the belt onto the alternator pulley. Slowly release the tensioner to apply proper tension. Verify the belt is properly seated in all pulley grooves.
12. 12

    Reconnect battery
    Clean battery terminal and cable end with battery terminal cleaner if necessary. Reconnect the negative battery cable to the negative battery terminal. Install and torque the terminal bolt to 6.0 Nm (4.0 lb-ft). Do not overtighten as this may damage the terminal.
    ⚠Battery terminal bolts are easily damaged by overtightening - use torque wrench
    Torque spec

    Battery Terminal Bolts8 Nm (6 lb-ft)
13. 13

    Reinstall engine cover
    Align the engine cover mounting grommets with the mounting posts and press down firmly until all grommets are fully seated.

Reassembly

1. Ensure all electrical connections are secure and properly seated
2. Verify serpentine belt is properly routed and seated in all pulley grooves
3. Confirm all tools and parts have been removed from engine bay

Verification

• Start the engine and verify the alternator is operating quietly without unusual noises
• Check that the battery charging light on the instrument cluster turns off after engine start
• Using a multimeter, verify charging voltage at battery terminals is between 13.5-14.5 volts at idle
• Observe serpentine belt operation to ensure it tracks properly without slipping or vibrating
• Test electrical accessories (headlights, radio, climate control) to verify proper alternator output under load
• Check for any warning lights on the instrument cluster

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