Engine Controls - Tests W/codes: Diagnosis Geo Tracker I

SELF-DIAGNOSTIC SYSTEM

Note. Tracker uses an Engine Control Module (ECM). All references to ECM include PCM unless specified otherwise.

TROUBLE CODE DEFINITIONS

FAULT CODE IDENTIFICATION

DIAGNOSTIC CODE CHARTS

Note. Following diagnostic flow charts and mini-schematics are courtesy of General Motors Corp.

DIAGNOSTIC CIRCUIT CHECK

Diagnostic circuit check is an organized approach in identifying a problem created by an electronic engine system malfunction. It must be the starting point for any driveability complaint diagnosis, because it directs the service technician to the next logical step in diagnosing a complaint. Understanding the chart and using it correctly will reduce diagnostic time and prevent unnecessary replacement of good parts.

Note. Test numbers refer to test numbers on diagnostic chart.

1. Checks Malfunction Indicator Light (MIL) operation.
2. Checks if ECM's self-diagnostic mode is operating.
3. Checks if ECM's serial data output is operating.
4. Checks if engine will start.
5. Checks for any codes that are stored in ECM memory with engine running.
6. Checks for any codes that are stored in ECM memory with engine off. If no codes are stored and engine will not start, see appropriate CHART A-3 in BASIC TESTING article in this section.
7. Compares ECM's control data to typical data values.
8. Checks if codes are intermittent problems. If engine will not start and no codes set while cranking, see appropriate CHART A-3 in BASIC TESTING article in this section.

Diagnostic Circuit Check - Schematic. Scheme 14

Diagnostic Circuit Check - Flow Chart. Scheme 15

Diagnostic Aids

Check connectors for contamination, corrosion or bent terminals.

Chart A-1 - Flow Chart No Malfunction Indicator Light. Scheme 16

On vehicles with Federal emissions, ensure MIL cancel switch is reset after 50,000, 80,000 and 100,000 maintenance service has been completed for MIL to go out.

Chart A-2 - Flow Chart Won't Flash Code 12 Or Any Codes, MIL On Steady. Scheme 17

Normal heated O2 sensor voltage is .1-.9 volt (varying) in closed loop operation.

Code 13 - Schematic Heated Oxygen Sensor Circuit. Scheme 18

Code 13 - Flow Chart Heated Oxygen Sensor Circuit. Scheme 19

After engine is started, temperature should rise steadily to about 203°F (95°C) and then level off when thermostat opens.

If Codes 14 and 21 are stored at same time, an open could exist in Gray/Yellow wire.

When replacing ECT sensor, check TEMPERATURE TO RESISTANCE VALUES table. A "shifted" sensor could result in poor driveability complaints.

Code 14 - Schematic Engine Coolant Temperature Sensor Circuit, Low Temp. Indicated. Scheme 20

Code 14 - Flow Chart Engine Coolant Temperature Sensor Circuit, Low Temp. Indicated. Scheme 21

After engine is started, temperature should rise steadily to about 203°F (95°C) and then level off when thermostat opens.

Ensure engine is not overheating and has not been subjected to conditions which would create an overheating condition (i.e., overload, trailer towing, heavy stop and go traffic, etc.).

When replacing ECT sensor, check TEMPERATURE TO RESISTANCE VALUES table. A "shifted" sensor could result in poor driveability complaints.

Code 15 - Flow Chart Engine Coolant Temperature Sensor Circuit, High Temp. Indicated. Scheme 22

A misadjusted TP sensor can cause a false Code 21 or 22 to set.

Code 21 - Schematic Throttle Position Sensor Circuit, Signal Voltage High. Scheme 23

Code 21 - Flow Chart Throttle Position Sensor Circuit, Signal Voltage High. Scheme 24

A misadjusted TP sensor can cause a false Code 21 or 22 to set. Codes 22 and 32 set at the same time could be the result of an open Gray/Red wire between ECM and TP sensor.

Code 22 - Flow Chart Throttle Position Sensor Circuit, Signal Voltage Low. Scheme 25

Codes 21 and 23 stored at the same time could be the result of an open in Gray/Yellow wire.

When replacing IAT sensor, check TEMPERATURE TO RESISTANCE VALUES table. A "shifted" sensor could result in poor driveability complaints.

Code 23 - Schematic Intake Air temperature Sensor Circuit, Low Temp. Indicated. Scheme 26

Code 23 - Flow Chart Intake Air temperature Sensor Circuit, Low Temp. Indicated. Scheme 27

If speedometer cable is binding, Code 24 can be set. Ensure that speedometer cable is free from restrictions and has a secure connection to instrument cluster. If problem is intermittent, refer to TESTS W/O CODES article in this section.

Code 24 - Schematic Vehicle Speed Sensor Circuit. Scheme 28

Code 24 - Flow Chart Vehicle Speed Sensor Circuit. Scheme 29

When replacing IAT sensor, check TEMPERATURE TO RESISTANCE VALUES table. A "shifted" sensor could result in poor driveability complaints.

Code 25 - Flow Chart IAT Sensor Circuit, High Temperature Indicated. Scheme 30

Check for leaking vacuum hose to MAP sensor.

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out, improperly mated, broken locks, improperly formed, or damaged terminals, and poor terminal-to-wire connections, and damaged harness.

Code 31 - Schematic MAP Sensor Circuit, High Voltage Input - High Vacuum. Scheme 31

Code 31 - Flow Chart MAP Sensor Circuit, High Voltage Input - High Vacuum. Scheme 32

Check for blocked or pinched vacuum hose to MAP sensor.

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out, improperly mated, broken locks, improperly formed, or damaged terminals, and poor terminal-to-wire connections, and damaged harness.

Codes 22 and 32 stored at the same time could be the result of an open in Gray/Red wire.

Code 32 - Flow Chart MAP Sensor Circuit, Low Voltage Input - High Vacuum. Scheme 33

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out, improperly mated, broken locks, improperly formed, or damaged terminals, and poor terminal-to-wire connections, and damaged harness.

Code 41 - Schematic Ignition Signal Circuit, No Signal. Scheme 34

Code 41 - Flow Chart (1 Of 2) Ignition Signal Circuit, No Signal. Scheme 35

Code 41 - Flow Chart (2 Of 2) Ignition Signal Circuit, No Signal. Scheme 36

A loose or damaged CMP sensor could cause an intermittent code. A misaligned crank angle sensor or improper air gap could set Code 42 or an intermittent no-start condition.

Code 42 - Schematic Camshaft Position Sensor. Scheme 37

Code 42 - Flow Chart Camshaft Position Sensor. Scheme 38

A misadjusted TP sensor could cause Code 44 to set. Before replacing TP sensor, check TP sensor adjustment. Refer to ADJUSTMENTS article in this section.

Code 44 - Flow Chart Idle Switch Circuit, Open Circuit Or Misadjusted. Scheme 39

A misadjusted TP sensor could cause Code 45 to set. Before replacing TP sensor, check TP sensor adjustment. Refer to ADJUSTMENTS article in this section.

Code 45 - Flow Chart Idle Switch Circuit, Circuit Grounded Or Misadjusted. Scheme 40

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out, improperly mated, broken locks, improperly formed, or damaged terminals, and poor terminal-to-wire connections, and damaged harness.

Code 51 - Schematic Exhaust Gas Recirculation Circuit. Scheme 41

Code 51 - Flow Chart Exhaust Gas Recirculation Circuit. Scheme 42

A poor ground connection could cause Code 53 to set. Ensure ground connection is clean and tight.

Code 53 - Schematic Ground Circuit, Circuit Open. Scheme 43

Code 53 - Flow Chart Ground Circuit, Circuit Open. Scheme 44