Powertrain Control Module Controlled Starter Diagnosis Functional Check
| Table 1: | Crank Relay |
Circuit Description
The PCM controlled starter system consists of the following components:
| • | The Ignition switch |
| • | The Crank Request circuit |
| • | The PCM |
| • | The Crank relay |
| • | The Transaxle Range switch |
| • | The Starter solenoid |
When the Ignition switch is turned to the Crank position, B+ is sent to the PCM via the Crank Request circuit. The PCM has the ability to disallow starter operation if conditions inappropriate for starter operation exist. The PCM will disable the starter under the following conditions:
| • | The engine is running |
| • | A correct VTD password is not received from the BCM |
| • | The vehicle operator continues to engage the starter for an extended period of time |
If no inhibiting conditions are present, and the PCM detects voltage on the Crank Request circuit, the PCM grounds the Crank Relay Control circuit. Current from the Crank maxifuse flows through the relay through the Transaxle Range switch (only in P/N) to the Starter solenoid.
Diagnostic Aids
This diagnostic procedure is intended to identify electrical malfunctions within the PCM controlled portion of the starting system. For additional system diagnosis, refer to Starting System Check in Electrical Diagnosis.
Use the Connector Test Adapter Kit J 35616 for any test that requires probing the PCM harness connectors, electrical center fuse/relay cavities, component terminals or a component harness connector. Using this kit will prevent damage caused by improper probing of connector terminals.
If the problem is intermittent, refer to Intermittent Conditions for diagnosis.
Relay Terminal Identification
Use the following relay cavity table in order to locate the correct cavities to probe during diagnosis. The table layout corresponds to the cavity layout in the Underhood Accessory Wiring Junction Block. Four blade relays can be inserted two ways. Use the table and NOT the numbering on the relay to avoid probing incorrectly.
Top of Junction Block | |
|---|---|
Switch Power (Crank MaxiFuse) | Coil Ground (PCM) |
Coil Power (Fuse) | Switch Load (Starter) |
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table:
-
Ensure that there are no problems with the battery or the battery connections before attempting starter diagnosis. If the battery required a charge, but was otherwise OK, check for a charging system problem or for a parasitic drain. Refer to Charging System Check or Battery Electrical Drain/Parasitic Load .
-
If the status of the Starter Enable Relay (Crank relay) indicates anything other than OK with the key in either position, there is a problem with the Crank relay control circuit.
-
Make sure that the transmission is in Park/Neutral.
-
Check for poor connections/terminal tension at the fuse. Refer to Intermittents and Poor Connections Diagnosis .
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | |||||||
|
Important: Check the battery connections. Fully charge and load test the battery before proceeding with starter diagnosis. Refer to Battery Not Operating Properly .Turn the key to Start. Does the Starter crank the engine? | -- | Refer to Diagnostic Aids. | Go to Step 3 | |||||||
3 |
Does the test lamp illuminate with the key in Start? | -- | The PCM Controlled portion of the starter circuit is functioning. Refer to Starting System Check in electrical diagnosis. | Go to Step 4 | ||||||
4 | Using the scan tool check for the following DTCs:
Are any VTD related DTCs set? | -- | Go to the applicable DTC table. | Go to Step 5 | ||||||
5 | Monitor Crank Request with the scan tool. Does scan tool indicate No with the key in the On position and Yes in Start? | -- | Go to Step 6 | |||||||
Does the status continuously indicate OK in both key positions? | -- | Go to Step 7 | Go to Powertrain Control Module Controlled Starter Diagnosis | |||||||
Ensure that the transmission gear selector lever is in Park. Does the starter operate with the key in On? | -- | Go to Step 20 | Go to Step 8 | |||||||
Check the Crank maxifuse. Is the fuse OK? | -- | Go to Step 14 | Go to Step 9 | |||||||
9 |
Is the resistance more than the specified value? | 2 Ohms | Go to Step 10 | Go to Step 22 | ||||||
10 |
Is the resistance more than the specified value? | 2 Ohms | Go to Step 12 | Go to Step 11 | ||||||
11 |
Is the resistance more than the specified value on either circuit? | 2 Ohms | Go to Step 26 | Go to Step 28 | ||||||
12 |
Is the fuse OK? | -- | Go to Step 13 | Go to Step 34 | ||||||
13 |
Is the fuse OK? | -- | Refer to Diagnostic Aids. | Go to Step 36 | ||||||
14 |
Is the test lamp on? | -- | Go to Step 15 | Go to Step 24 | ||||||
15 | Jumper the B+ feed circuit to the Starter Solenoid Control circuit in the relay connector. Does the starter operate? | -- | Go to Step 33 | Go to Step 16 | ||||||
16 |
Is the test lamp on? | -- | Go to Step 17 | Go to Step 25 | ||||||
17 |
Does the starter operate? | -- | Go to Step 27 | Go to Step 18 | ||||||
18 |
Is the test light on? | -- | Go to Step 35 | Go to Step 19 | ||||||
19 |
Is the test light on? | -- | Go to Step 32 | Go to Step 25 | ||||||
20 |
Does the Starter operate with the key in On? | -- | Go to Step 21 | Go to Step 30 | ||||||
21 | Disconnect the Crank relay. Does the Starter operate with the key in On? | -- | Go to Step 29 | Go to Step 34 | ||||||
22 | Repair the short to ground in the B+ feed circuit to the relay. Is the action complete? | -- | Go to Step 37 | -- | ||||||
23 | Repair the short to ground in the solenoid control circuit. Is the action complete? | -- | Go to Step 37 | -- | ||||||
24 | Repair the open/high resistance B+ feed circuit to the relay. Is the action complete? | -- | Go to Step 37 | -- | ||||||
25 | Repair the open/high resistance solenoid control circuit. Is the action complete? | -- | Go to Step 37 | -- | ||||||
26 | Repair the affected circuit shorted to ground. Is the action complete? | -- | Go to Step 37 | -- | ||||||
27 | Check for the following conditions:
Was a problem found and corrected? | -- | Go to Step 37 | Go to Step 28 | ||||||
28 | Replace the Transaxle Range switch. Is the action complete? | -- | Go to Step 37 | -- | ||||||
29 | Check for the following conditions and repair as necessary:
Is the action complete? | -- | Go to Step 37 | -- | ||||||
30 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete | -- | Go to Step 37 | -- | ||||||
31 | Replace the Crank relay. Is the action complete? | -- | Go to Step 37 | -- | ||||||
32 | Check for a loose solenoid/starter motor or mounting surface corrosion causing a loss of ground continuity. Repair as necessary. Is the action complete? | -- | Go to Step 37 | -- | ||||||
33 | Check for poor connections/terminal tension at the relay connector. Refer to Intermittents and Poor Connections Diagnosis . Was a problem found and corrected? | -- | Go to Step 37 | Go to Step 34 | ||||||
34 | Replace the Crank relay. Is the action complete? | -- | Go to Step 37 | -- | ||||||
35 | Check for poor connections/terminal tension at the Starter Solenoid. Refer to Intermittents and Poor Connections Diagnosis . Was a problem found and corrected? | -- | Go to Step 37 | Go to Step 36 | ||||||
36 | Replace the Starter Solenoid. Is the action complete? | -- | Go to Step 37 | -- | ||||||
37 | Turn the key to Start. Does the Starter operate? | -- | System OK | Go to Step 2 |
Powertrain Control Module Controlled Starter Diagnosis Crank Relay Control Circuit
| Table 1: | Crank Relay |
Circuit Description
Ignition Voltage is supplied directly to the Crank relay. The PCM controls the relay by grounding the control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the PCM. When the PCM is commanding a component on, the voltage of the control circuit should be low (near 0 volts). When the PCM is commanding the control circuit to a component off, the voltage potential of the circuit should be high (near battery voltage). Driver status can be monitored using a scan tool. If the fault detection circuit senses a voltage other than what is expected, the driver status will change from OK to Fault.
The PCM will monitor the control circuit for the following:
| • | A short to ground |
| • | A short to voltage |
| • | An open circuit |
| • | An open relay coil |
| • | An internally shorted or excessively low resistance relay coil. |
Diagnostic Aids
Use the Connector Test Adapter Kit J 35616 for any test that requires probing the PCM harness connectors, electrical center fuse/relay cavities, component terminals or a component harness connector. Using this kit will prevent damage caused by improper probing of connector terminals.
If the problem is intermittent, refer to Intermittent Conditions for diagnosis.
Relay Terminal Identification
Use the following relay cavity table in order to locate the correct cavities to probe during diagnosis. The table layout corresponds to the cavity layout in the Underhood Accessory Wiring Junction Block. Four blade relays can be inserted two ways. Use the table and NOT the numbering on the relay to avoid probing incorrectly.
Top of Junction Block | |
|---|---|
Switch Power (Crank MaxiFuse) | Coil Ground (PCM) |
Coil Power (Fuse) | Switch Load (Starter) |
Test Description
The number(s) below refer to the step numbers on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the PCM Controlled Starter Diagnosis Functional Check? | -- | Go to Powertrain Control Module Controlled Starter Diagnosis | |
2 |
Is the test light off with the key in On and on with the key in Start? | -- | ||
3 |
Does the test light illuminate? | -- | ||
4 | Probe the control circuit to the relay coil in the relay harness connector with the test light connected to B+. Does the test light illuminate? | -- | ||
5 |
Does the test light illuminate? | -- | ||
6 |
Does the relay operate? | -- | ||
7 | Check for poor connections/terminal tension at the relay harness connector. Refer to Intermittents and Poor Connections Diagnosis . Was a problem found and corrected? | -- | ||
8 | Repair the relay control circuit. Is the action complete? | -- | -- | |
9 | Repair the Ignition feed circuit to the relay coil. Is the action complete? | -- | --
| |
10 | Replace the relay. Is the action complete? | -- | -- | |
11 | Check for poor connections/terminal tension at the PCM harness connector. Refer to Intermittents and Poor Connections Diagnosis . Was a problem found and corrected? | -- | ||
Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
13 |
Does the scan tool indicate that this test ran and passed? | -- | ||
14 | Review Captured Info using the scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to the applicable DTC table | System OK |
