How To Test The Starter Motor (1995-1999 3.1L V6 Chevrolet Lumina, Monte Carlo)

TEST 3: Voltage Drop Testing The Battery Wire

Up to this point, you have verified that:

• The battery is fully charged and its terminals are clean.
• The starter motor cranks the engine when you directly applied 12 Volts to its S terminal with a remote start switch (TEST 1).

The next step is to make sure that the positive (+) battery cable that attaches to the starter motor's solenoid is supplying full battery voltage and amperage to the starter motor.

In other words, we need to make sure that there isn't any hidden corrosion somewhere on the cable holding back any battery power to the starter motor.

We'll accomplish this check for 'hidden corrosion' by doing a simple voltage drop test.

IMPORTANT: The battery must remain connected to its two battery cables for the voltage drop test to work.

These are the test steps:

1. 1

   Connect the red multimeter test lead to the center of the bolt that attaches to the positive (+) battery cable to the battery.
   
   The spot on this bolt, which the multimeter test lead will be touching, has to be clean and rust-free.
   
   NOTE: You may need two helpers for this test step, since someone will have to hold the red multimeter test lead onto the battery positive (+) terminal bolt and someone else inside the vehicle (to turn the key and attempt to crank the engine when everything is set up).

2. 2

   With the black multimeter test lead, touch the center of the starter solenoid stud that connects to the positive (+) battery cable.
   
   The orange arrow with the letter B, in the photo above, points to this starter motor solenoid stud.
   
   IMPORTANT: Maintain the black multimeter test lead in this position throughout the next step.

3. 3

   When everything is ready, have your helper crank the engine from the ignition switch.
   
   Although the starter motor won't crank the engine, your helper has to turn the key to 'START' for the voltage drop test to work.

4. 4

   The multimeter should register 0.5 Volts or less (0.5 V is really 0 Volts)
   
   If there's a problem in the wire (like corrosion or a loose connection), your multimeter will register a voltage of 5 Volts or more.

Let's take a look at what your results mean:

CASE 1: Your multimeter indicated NO voltage drop (which is 0.5 Volts or less). This result indicates that the starter motor is receiving all of the battery voltage/amperage it needs to crank the engine.

This result also confirms that the starter motor is bad and needs to be replaced if you have confirmed:

• That the starter motor DOES NOT crank the engine when you pass 12 Volts directly to it (TEST 1).
• That the battery cable, that attaches to the starter motor solenoid does not have a voltage drop (this test section).

Now, before you remove the starter motor, do two more things:

1.) Turn the engine manually (using a 1/2 ratchet and the appropriate socket on the crankshaft pulley) to make sure that the engine is not mechanically locked up.

2.) Bench test the starter motor. You can find the step-by-step instructions here: How To Bench Test A Starter Motor (Step By Step).

CASE 2: Your multimeter registered 5 Volts or more. This result tells you that a voltage drop does exist and as a result, the starter motor is not receiving all of the voltage/amperage it needs to crank the engine.

The solution is to simply disconnect the positive (+) battery cable from the battery and thoroughly clean it.

Also, the end of this very same cable, that's attached to the starter motor solenoid, should be disconnected, inspected and cleaned.

Cleaning the end that attaches to the starter motor solenoid should be done with a small piece of sand paper. Once both ends of the battery positive cable are clean, reconnect everything and try cranking the engine.

If the voltage drop was the cause of the engine's no-crank condition, your vehicle will now crank and start.

TEST 4: Testing The START Signal (Anti-Theft Relay)

So far you have:

• Confirmed that the starter motor does crank the engine but only when using a remote start switch (TEST 1).
• That the starter motor is not receiving a START signal (TEST 2).

In this test section, we're gonna' make sure that the anti-theft relay is receiving 10 to 12 Volts DC from the ignition switch.

Specifically, we'll be making sure that the female terminal labeled A2, of the anti-theft relay's electrical connector, has 10 to 12 Volts when turning the key to the START position.

To find the location of the anti-theft relay, see this section: Location Of The Anti-Theft Relay.

Let's get testing:

1. 1

   Locate and remove from the anti-theft relay from its location.

2. 2

   Disconnect the anti-theft relay from its connector.

3. 3

   Place your multimeter in Volts DC mode.

4. 4

   Connect the black multimeter test lead to the battery negative (-) terminal.

5. 5

   With the red multimeter test lead, probe the female terminal labeled A2 in the photo above.

6. 6

   Have your helper turn the key to the START position.

7. 7

   Your multimeter should register 10 to 12 Volts DC.

Let's examine your test result:

CASE 1: The multimeter registered 10 to 12 Volts. This is the correct test result.

With this test result you can conclude that the ignition switch is OK and sending the START signal to terminal A2.

Your next test is to check that the park-neutral safety switch is functioning correctly. Go to: TEST 5: Testing The Park-Neutral Safety Switch Signal (Anti-Theft Relay).

CASE 2: The multimeter DID NOT register 10 to 12 Volts. This test result usually tells you that the ignition switch is not sending a START signal to the anti-theft relay.

The most likely cause of this missing 12 Volts DC is a bad ignition switch.

TEST 5: Testing The Park-Neutral Safety Switch Signal (Anti-Theft Relay)

In the previous test you confirmed that the ignition switch is sending 12 Volts to terminal A2 of the anti-theft relay's connector.

Now we're gonna' check that female terminal labeled C2 has 10 to 12 Volts when turning the key to the START position.

If 10 to 12 Volts are not present in the C2 terminal, then you can conclude that the park/neutral safety switch has a problem (and behind the starter motor's no-crank issue).

Let's get testing:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Connect the black multimeter test lead to the battery negative (-) terminal.

3. 3

   With the red multimeter test lead, probe the female terminal labeled C2 in the photo above.

4. 4

   Have your helper turn the key to the START position.

5. 5

   Your multimeter should register 10 to 12 Volts DC.

Let's examine your test result:

CASE 1: The multimeter registered 10 to 12 Volts. This is the correct test result.

With this test result you can conclude that the automatic transmission's park/neutral safety switch is OK.

Your next step is to bypass the anti-theft relay with a jumper wire. For this test go to: TEST 6: Bypassing The Anti-Theft Relay.

CASE 2: The multimeter DID NOT register 10 to 12 Volts. This missing voltage, from the park/neutral safety switch, will cause the anti-theft relay to not activate and the starter motor will not crank the engine.

The most likely cause of these missing 12 Volts are:

• Fuse 11 of the dash panel fuse box is blown (1995-1997 Lumina and Monte Carlo).
• Fuse 7 of the dash panel fuse box is blown (1998-1999 Lumina and Monte Carlo).
• A misadjusted park/neutral safety switch.
• A bad park/neutral safety switch.
• A damaged park/neutral safety switch.
• The park/neutral safety switch connector is loose, broken, or damaged.

Your next step is to check Fuse 7 (or Fuse 11) of the dash panel fuse box. If it's blown, replace it and repeat the test.

If the fuse is not blown, your next step is to test the automatic transmission's park/neutral safety switch.