Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Mazda B4000, 2003 Mazda B3000, and 2003 Mazda B2300. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Vehicles with 2.3L engine are equipped with a Cylinder Head Temperature (CHT) sensor. Vehicles with 3.0L or 4.0L engine are equipped with an Engine Coolant Temperature (ECT) sensor. All vehicles are equipped with a Mass Airflow/Intake Air Temperature (MAF/IAT) sensor.

If QUICK TEST was not performed, go to QUICK TEST under SELF-DIAGNOSTIC SYSTEM. If QUICK TEST was performed:
- For DTC P1116 or P1288, go to next step.
- For DTC P1285 (if not cooling system malfunction), go to step 4 .
- For KOEO or KOER DTCs P0113 or P0118, go to step 6 .
- For DTC P1289 or P1290, go to step 10 .
- For Continuous Memory (without KOEO and KOER DTCs) DTC P0112, P0113, P0117, P0118, P1112 or P1117, go to step 14 .
- For DTC P0125, go to step 16 .
- For DTC P1299, go to step 17 .
DTC P1116, P1288: Check Operation Of ECT Or CHT Sensor - Run engine at 2000 RPM until engine temperature stabilizes. If vehicle does not start, go to step 4 . If vehicle stalls, see TROUBLE SHOOTING - NO CODES article. Verify upper radiator hose is hot and pressurized. Run KOER self-test. If DTC P1116 or P1288 is set, go to next step. If DTC P1116 or P1288 is not set, engine was not in closed loop operating conditions. Repair any other DTCs as necessary.
Check VREF Circuit Voltage At TP Sensor - Turn ignition off. Disconnect Throttle Position (TP) sensor 3-pin harness connector. With KOEO, measure voltage between VREF circuit (Brown/White wire) and SIG RTN circuit (Gray/Red wire) at TP sensor connector. See Fig 1 . If voltage reading is 4-6 volts, go to next step. If voltage reading is not 4-6 volts, go to VEHICLE REFERENCE VOLTAGE testing under SYSTEM TESTS.

Fig 1: Identifying TP Sensor Circuits
Courtesy of MAZDA MOTORS CORP.

Check Resistance Of Temperature Sensor With Engine Off - Turn ignition off. Reconnect TP sensor 3-pin harness connector. Disconnect ECT or CHT sensor 2-pin harness connector. Measure resistance between ECT circuit (Light Green/Red wire) or CHT circuit (Yellow/Light Green wire) and SIG RTN circuit (Gray/Red wire) at sensor harness connector. See Fig 2 or Fig 3 . See ECT & IAT SENSOR SPECIFICATIONS or CHT SENSOR SPECIFICATIONS table. If resistance reading is within specifications, for ECT or CHT sensor with a no start (do not service DTC P1116 at this time), see TROUBLE SHOOTING - NO CODES article. For symptoms of cooling fan concerns, overheating or lack of heat (do not service DTC P1116 or P1288 at this time) repair next DTC. If no other DTCs are set, see appropriate COOLING SYSTEM SPECIFICATIONS & DRIVE BELT ROUTING article in ENGINES. Repair cooling system malfunction as necessary. For all other conditions, go to next step. If resistance reading is not within specifications, replace suspect ECT or CHT sensor. After repair, go to step 16 .

Fig 2: Identifying ECT Sensor Circuits (3.0L & 4.0L)

Courtesy of MAZDA MOTORS CORP.

Fig 3: Identifying CHT Sensor Circuits (2.3L)

Courtesy of MAZDA MOTORS CORP.

ECT & IAT SENSOR SPECIFICATIONS ⁽¹⁾

Temperature °F (°C)

Volts

⁽²⁾ Ohms

50 (10)

3.51

58,750

68 (20)

3.07

27,300

86 (30)

2.60

24,270

104 (40)

2.13

16,150

122 (50)

1.70

10,970

140 (60)

1.33

7700

158 (70)

1.02

5370

176 (80)

0.78

3840

194 (90)

0.60

2800

212 (100)

0.46

2070

230 (110)

0.35

1550

248 (120)

0.27

1180

⁽¹⁾	Values may differ by as much as 15 percent.

⁽²⁾	Measure resistance between sensor terminals.

CHT SENSOR SPECIFICATIONS

Temperature °F (°C)

Volts

⁽¹⁾ Ohms

-40 (-40)

4.89

965,808

-22 (-30)

4.81

513,019

-4 (-20)

4.67

283,664

14 (-10)

4.45

162,584

32 (0)

4.14

96,255

50 (10)

3.73

59,175

68 (20)

3.26

37,387

86 (30)

2.74

24,215

104 (40)

2.23

16,043

122 (50)

1.76

10,850

140 (60)

1.36

7487

158 (70)

1.04

5268

176 (80) ⁽²⁾

0.79 Or 3.99

3775

185 (85) ⁽²⁾

0.69 Or 3.86

3215

194 (90) ⁽²⁾

0.60 Or 3.71

2750

203 (95) ⁽²⁾

0.53 Or 3.56

2361

212 (100) ⁽²⁾

0.46 Or 3.41

2034

230 (110)

3.07

1523

248 (120)

2.74

1155

266 (130)

2.41

887

284 (140)

2.10

689

302 (150)

1.81

542

320 (160)

1.55

430

338 (170)

1.33

345

356 (180)

1.13

279

374 (190)

0.96

228

392 (200)

0.82

188

410 (210)

0.70

155

428 (220)

0.60

130

446 (230)

0.51

109

464 (240)

0.44

482 (250)

0.35

500 (260)

0.33

⁽¹⁾	Measure resistance between cylinder head temperature sensor terminals.

⁽²⁾	At this temperature, there is a voltage overlap zone where it is possible to have either a cold end (low voltage) or hot end (high voltage) reading at the same temperature. Either voltage specification listed is correct.

Check Resistance Of Temperature Sensor With Engine Running - Verify engine is at normal operating temperature. Turn ignition off. Disconnect suspect temperature sensor harness connector. Run engine at 2000 RPM for 2 minutes. Measure resistance between ECT circuit (Light Green/Red wire) or CHT circuit (Yellow/Light Green wire) and SIG RTN circuit (Gray/Red wire) at sensor harness connector. See Fig 2 or Fig 3 . If resistance reading is within specifications, replace faulty PCM. After repair, go to step 16 . If resistance reading is not within specifications, replace faulty ECT or CHT sensor. After repair, go to step 18 .
DTCs P0113 Or P0118: Check Voltage Between VREF & SIG RTN - Turn ignition off. Disconnect TP sensor 3-pin harness connector. With KOEO, measure voltage between VREF circuit (Brown/White wire) and SIG RTN circuit (Gray/Red wire) at TP sensor harness connector. See Fig 1 . If voltage reading is 4-6 volts, go to next step. If voltage reading is not 4-6 volts, go to VEHICLE REFERENCE VOLTAGE testing under SYSTEM TESTS.
Simulate Opposite Signal To PCM - Turn ignition off. Disconnect suspect temperature sensor. Connect a fused jumper wire between ECT sensor circuit (Light Green/Red wire), CHT sensor circuit (Yellow/Light Green wire) or IAT sensor circuit (Gray wire) and SIG RTN circuit (Gray/Red wire) at appropriate sensor harness connector. See Fig 2 , Fig 3 or Fig 4 . With KOEO, access ECT V PID, CHT V PID or IAT V PID and observe. If a scan tool communication concern is present, remove fused jumper wire and go to step 9 . If voltage reading is 0.2 volt or more, remove fused jumper wire and go to next step. If voltage reading is less than 0.2 volt, remove fused jumper wire and replace suspect sensor. After repair, go to step 18 .

Fig 4: Identifying MAF/IAT Sensor Circuits
Courtesy of MAZDA MOTORS CORP.
Check Temperature Sensor Signal & SIG RTN Circuits For Open In Harness - Turn ignition off. Disconnect PCM 104-pin harness connector. Disconnect suspect temperature sensor. Connect breakout box to PCM harness connector only. See Figure . Measure resistance between ECT sensor circuit (Light Green/Red wire), CHT sensor circuit (Yellow/Light Green wire) or IAT sensor circuit (Gray wire) and breakout box terminal No. 38 (ECT circuit), terminal No. 66 (CHT circuit) or terminal No. 39 (IAT circuit). See Fig 2 , Fig 3 or Fig 4 . Record reading. Measure resistance between SIG RTN circuit (Gray/Red wire) at appropriate temperature sensor connector and breakout box terminal No. 91. Record reading. If each measurement reading is less than 5 ohms, replace faulty PCM. Go to step 18 . If each measurement reading is 5 ohms or more, repair open circuit. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, go to step 18 .
Check Temperature Sensor Signal & SIG RTN Circuits For Short To VREF In Harness - Measure resistance between SIG RTN circuit (Gray/Red wire) at appropriate temperature sensor connector and breakout box terminal No. 90 (VREF circuit). See Fig 2 , Fig 3 or Fig 4 . If resistance reading is more than 10,000 ohms, replace faulty PCM. If resistance reading is 10,000 ohms or less, repair short to VREF circuit. After repair, go to step 18 .
DTCs P1289 Or P1290: Check Voltage Of CHT Sensor - With KOEO, access CHT V PID and observe. If voltage reading is less than 0.2 volt, go to next step. If voltage reading is 0.2 volt or more, go to step 7 .
DTCs P0112 Or P0117: Simulate Opposite Signal To PCM - Turn ignition off. Disconnect suspect temperature sensor. With KOEO, access ECT V PID, CHT V PID or IAT V PID and observe. If voltage reading is 4.6 volts or less, go to next step. If voltage reading is more than 4.6 volts, replace faulty temperature sensor. After repair, go to step 18 .
Check VREF Circuit Voltage To TP Sensor - Turn ignition off. Disconnect TP sensor 3-pin harness connector. With KOEO, measure voltage between VREF circuit (Brown/White wire) and SIG RTN circuit (Gray/Red wire) at TP sensor 3-pin harness connector. See Fig 1 . If voltage reading is 4-6 volts, there is sufficient VREF voltage. Reconnect TP sensor 3-pin harness connector and go to next step. If voltage reading is not 4-6 volts, reconnect TP sensor 3-pin harness connector and go to VEHICLE REFERENCE VOLTAGE testing under SYSTEM TESTS.
Check Signal Circuit For Short To Ground In Harness - Turn ignition off. Disconnect suspect temperature sensor. Connect breakout box to PCM harness connector only. See Figure . Measure resistance between breakout box terminal No. 38 (ECT circuit), terminal No. 66 (CHT circuit) or terminal No. 39 (IAT circuit) and terminal No. 24 (PWR GND circuit). See Fig 2 , Fig 3 or Fig 4 . Record reading. Measure resistance between breakout box terminal No. 38 (ECT circuit), terminal No. 66 (CHT circuit) or terminal No. 39 (IAT circuit) and terminal No. 91 (SIG RTN circuit). Record reading. If each resistance reading is more than 10,000 ohms, replace faulty PCM. After repair, go to step 18 . If each resistance reading is 10,000 ohms or less, repair short circuit. After repair, go to step 18 .
DTCs P0112, P1112, P0113, P0117, P1117 Or P0118, P1289, P1290: Intermittent Check - With KOEO, monitor ECT V PID, CHT V PID or IAT V PID. While observing PID, tap on suspect sensor to simulate road shock and wiggle sensor harness connector. If any large change in temperature reading is not present, go to next step. If any large change in temperature reading is present, disconnect sensor harness connector and inspect. If sensor connector is okay, replace suspect sensor. After repair, go to step 16 . For Continuous Memory DTCs P1112 and P1117, perform COMPREHENSIVE COMPONENT MONITOR REPAIR VERIFICATION DRIVE CYCLE under MONITOR REPAIR VERIFICATION DRIVE CYCLES.
Check Engine Wiring Harness - Turn ignition on. While observing ECT V PID, CHT V PID or IAT V PID, grasp suspect sensor harness and harness connector and wiggle, shake and bend harness back to PCM. If no large change in temperature reading is present, go to next step. If any large change in temperature reading is present, isolate and repair fault as necessary. After repair, go to step 18 . For Continuous Memory DTCs P1112 and P1117, perform COMPREHENSIVE COMPONENT MONITOR REPAIR VERIFICATION DRIVE CYCLE under MONITOR REPAIR VERIFICATION DRIVE CYCLES.
DTC P0125 Indicates Excessive Time To Enter Closed Loop Fuel Control - Check engine coolant level. If coolant level is okay, repair cooling system malfunction as necessary. See appropriate COOLING SYSTEM SPECIFICATIONS & DRIVE BELT ROUTING article in ENGINES. If coolant level is not okay, fill to proper level. After repair, go to step 18 . For Continuous Memory DTCs P1112 and P1117, perform COMPREHENSIVE COMPONENT MONITOR REPAIR VERIFICATION DRIVE CYCLE under MONITOR REPAIR VERIFICATION DRIVE CYCLES.
DTC P1299 Indicates An Engine Overheat Condition Occurred - Check engine coolant level. If coolant level is okay, repair cooling system overheating condition as necessary. See appropriate COOLING SYSTEM SPECIFICATIONS & DRIVE BELT ROUTING article in ENGINES. If coolant level is not okay, repair cooling system leak.
Verify Trouble Shooting Of DTCs Completed - Make sure all electrical connectors are reconnected. Clear DTCs from PCM memory using scan tool. Perform QUICK TEST under SELF-DIAGNOSTIC SYSTEM. If the same DTC is present, replace faulty PCM. Repeat QUICK TEST under SELF-DIAGNOSTIC SYSTEM. If any other DTC is present, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are present, test is complete.