Starting System

Special Tool(s)

	Flex Probe Kit NUD105-R025D or equivalent
	Fluke 77-IV Digital Multimeter FLU77-4 or equivalent

Principles of Operation

The starting system is electronically controlled by the PCM. The PCM receives the following inputs:

• Correctly coded ignition key, from the Passive Anti-Theft System (PATS)
• Clutch pedal applied, from the Clutch Pedal Position (CPP) switch, vehicles with manual transmission
• Transmission in PARK or NEUTRAL, from the digital Transmission Range (TR) sensor, vehicles with automatic transmission
• Starter motor request, ignition switch in the START position

When the ignition switch is placed in the START position, a starter motor request signal is also sent to the PCM. If the PCM recognizes the correct input signals, it provides the starter relay coil with both voltage and ground. The starter relay contacts close, providing voltage to the starter solenoid, allowing the starter motor to activate.

Vehicles equipped with an automatic transmission have a digital TR sensor. The TR sensor prevents operation of the starter motor unless the transmission is in NEUTRAL or PARK.

Vehicles equipped a manual transmission have a CPP switch. The CPP switch prevents operation of the starter motor unless the clutch pedal is fully pressed.

Inspection and Verification

 WARNING: Always disconnect the battery ground cable at the battery before disconnecting the starter motor battery terminal lead. If a tool is shorted at the starter motor battery terminal, the tool can quickly heat enough to cause a skin burn. Failure to follow this instruction may result in serious personal injury.

NOTE: The anti-theft system must be functioning correctly before a logical starting system diagnosis can be carried out. Address anti-theft system concerns before continuing. Refer to Section 419-01B .

1. Verify the customer concern by operating the starting system.

2. Remove the accessory drive belt. Refer to Section 303-05 . Verify the crankshaft and each of the components driven by the accessory drive belt rotate and are not seized or damaged.

3. Visually inspect for obvious signs of mechanical and electrical damage. Refer to the following chart:

  Visual Inspection Chart

4. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.

5. NOTE: Make sure to use the latest scan tool software release.

   If the cause is not visually evident, connect the scan tool to the Data Link Connector (DLC).

6. NOTE: The Vehicle Communication Module (VCM) LED prove out confirms power and ground from the DLC are provided to the VCM .

   If the scan tool does not communicate with the VCM :
   • check the VCM connection to the vehicle.
   • check the scan tool connection to the VCM .
   • refer to Section 418-00 , No Power To The Scan Tool, to diagnose no power to the scan tool.

7. If the scan tool does not communicate with the vehicle:
   • verify the ignition key is in the ON position.
   • verify the scan tool operation with a known good vehicle.
   • refer to Section 418-00 to diagnose no response from the PCM.

8. Carry out the network test.
   • If the scan tool responds with no communication for one or more modules, refer to Section 418-00 .
   • If the network test passes, retrieve and record Continuous Memory Diagnostic Trouble Codes (CMDTCs).

9. Clear the continuous DTCs and carry out the self-test diagnostics for the PCM.

10. If the DTCs retrieved are related to the concern, go to PCM DTC Chart. For all other DTCs, refer to Section 419-10 .

11. If no DTCs related to the concern are retrieved, GO to Symptom Chart .

DTC Chart

 PCM DTC Chart

Symptom Chart

Pinpoint Tests

Pinpoint Test A: The Engine Does Not Crank

Refer to Wiring Diagrams Cell 20 , Starting System for schematic and connector information.

NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

Normal Operation

When the ignition switch is turned to the START position, the PCM receives a starter motor request signal. Voltage is supplied to the starter relay from the PCM. The PCM receives a signal from the digital Transmission Range (TR) sensor that the vehicle is in PARK or NEUTRAL (vehicles equipped with an automatic transmission) or from the Clutch Pedal Position (CPP) switch when the clutch pedal is fully depressed (vehicles equipped with manual transmission). A ground is supplied from the PCM causing the starter relay coil to energize and the relay contacts to close. This allows voltage to be supplied from Battery Junction Box (BJB) fuse 19 (30A) to the relay contacts, which then flows to the starter solenoid. The solenoid is grounded at the starter motor. Energizing the starter solenoid engages the starter drive into the ring gear and closes the solenoid contacts allowing voltage directly from the battery to the starter motor to start the engine. The PCM will disengage the starter motor based on engine running (rpm threshold), a set crank time has been exceeded or the ignition switch has been turned to the OFF position.

• DTC P0512 (Starter Request Circuit) — this DTC sets when the PCM detects an open or short to ground on the starter request circuit.

This pinpoint test is intended to diagnose the following:
• Anti-theft system
• Fuse
• Battery
• Battery cables
• Wiring, terminals or connectors
• CPP (manual transmission)
• Ignition switch
• PCM
• Starter motor
• Starter motor relay
• Digital TR sensor (automatic transmission)

PINPOINT TEST A: THE ENGINE DOES NOT CRANK

Pinpoint Test B: Unusual Starter Noise

Refer to Wiring Diagrams Cell 20 , Starting System for schematic and connector information.

Normal Operation

Correct starter operation relies on correct mounting of the starter to the engine, alignment of the starter ring gear to the flywheel or flexplate and correct functioning of the starter assembly (internal gears, bearings).

This pinpoint test is intended to diagnose the following:
• Starter motor
• Starter motor mounting
• Starter motor engagement
• Flywheel or flexplate ring gear

PINPOINT TEST B: UNUSUAL STARTER NOISE

Component Tests

 WARNING: Always disconnect the battery ground cable at the battery before disconnecting the starter motor battery terminal lead. If a tool is shorted at the starter motor battery terminal, the tool can quickly heat enough to cause a skin burn. Failure to follow this instruction may result in serious personal injury.

Always make the Fluke 77-IV Digital Multimeter connections at the component terminal rather than at the wiring end connector. Making a connection at the wiring end connector could result in false readings because the meter will not pick up a high resistance between the wiring connector and the component.

Starter Motor — Motor Feed Circuit

1. Make sure the battery is fully charged; carry out a Battery Condition Test. Refer to Section 414-01 .

2. Connect a remote starter switch between the starter solenoid S-terminal and the battery positive (+) terminal.

3. Connect the Fluke 77-IV Digital Multimeter positive lead to the battery positive (+) post. Connect the negative lead to the starter solenoid M-terminal.

4. Engage the remote starter switch. Read and record the voltage. The voltage reading should be 0.5 volt or less.

5. If the voltage reading is 0.5 volt or less, go to the Starter Motor — Ground Circuit component test.

6. If the voltage reading is greater than 0.5 volt, this is an indication of excessive resistance in the connections, the positive battery cable or in the starter solenoid. Move the Fluke 77-IV Digital Multimeter negative lead to the starter solenoid B-terminal and repeat the test. If the voltage reading at the B-terminal is lower than 0.5 volt, the concern is either in the connections at the starter solenoid or in the solenoid contacts.

7. Remove the cables from solenoid B, S and M-terminals. Clean the cables and connections and reinstall the cables to the correct terminals. Repeat Steps 3 through 6. If the voltage drop reading is still greater than 0.5 volt when checked at the M-terminal and less than 0.5 volt when checked at the B-terminal, the concern is in the solenoid contacts. Install a new starter motor.

8. If the voltage reading taken at the solenoid B-terminal is still greater than 0.5 volt after cleaning the cables and connections at the solenoid, the concern is either in the positive (+) battery cable connection or in the positive battery cable itself.

9. Clean the positive (+) battery cable connection. If this does not solve the problem, install a new positive battery cable.

Starter Motor — Ground Circuit

A slow cranking condition can be caused by resistance in the ground or return portion of the cranking circuit. Check the voltage drop in the ground circuit as follows:

1. Connect the Fluke 77-IV Digital Multimeter positive lead to the starter motor housing (the connection must be clean and free of rust or grease). Connect the negative lead to the negative (-) battery terminal.

2. Engage the remote starter switch and crank the engine. Read and record the voltage reading. The reading should be 0.5 volt or less.

3. If the voltage drop is more than 0.5 volt, clean the negative cable connections at the battery, the body ground connections and the starter ground connection. Retest.

4. If the voltage drop is greater than 0.5 volt, install a new cable. If the voltage reading is less than 0.5 volt and the engine still cranks slowly, install a new starter motor. INSTALL a new starter motor. REFER to Starter Motor — 3.7L or Starter Motor — 5.0L (4V) or Starter Motor — 5.8L (4V) . TEST the system for normal operation.