SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSMAZDA1999626 ES, 2.5 D, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 492 (SYMPTOM TROUBLESHOOTING [ENGINE CONTROL SYSTEM BP, BP WITH TC))NO.17 COOLING SYSTEM CONCERNS-OVERHEATINGDIAGNOSTIC PROCEDURE
1999 Mazda 626 ES, 2.5 D, Standard

Diagnostic Procedure

1999 Mazda 626 ES, 2.5 D, StandardSECTION Diagnostic Procedure
WARNING: This page is about a different car, the 2005 Mazda MX-5 Miata. However, it is still accessible from the selected car via links, so may be relevant.
NO.17 COOLING SYSTEM CONCERNS-OVERHEATING [BP, BP WITH TC] DIAGNOSTIC PROCEDURE

STEP INSPECTION ACTION
1
  • Inspect following:
    • Engine coolant level
    • Coolant leakage
    • Water and anti-freeze mixture
    • Radiator condition
    • Collapsed or restricted radiator hoses
    • Radiator pressure cap
    • Overflow system
    • Fan rotational direction
    • Fuses
  • Are all items okay?
 Yes Go to the next step.
No Service if necessary.
Repeat Step 1.
2
  • Connect WDS or equivalent to DLC-2.
  • Turn ignition switch to ON.
  • Retrieve any DTC.
  • Is "PASSED" displayed?
 Yes No DTC displayed: 
  • Go to the next step.
No DTC displayed: 
  • Go to appropriate DTC test.
3
  • Start engine and run it at idle speed.
  • Turn A/C switch on.
  • Does A/C compressor engage?
 Yes Go to Step 4.
No Inspect following and repair or replace if necessary:
  • Refrigerant charging amount
  • Open circuit between A/C magnetic clutch relay and PCM terminal 2K
  • Seized A/C magnetic clutch
  • A/C magnetic clutch malfunction
    • If all items are okay, inspect for following:
      • A/C pressure switch operation
      • A/C switch is stuck open
      • Open or short circuit between A/C pressure switch and PCM terminal 4F
      • Open circuit of blower motor fan switch and resistor (if blower motor does not operate)
      • Evaporator temperature sensor and amplifier
4
  • Start engine and run it at idle speed.
  • Turn A/C switch on.
  • Do condenser fan and main cooling fan operate?
 Yes Go to the next step.
No
  • If condenser fan does not operate, inspect for following: 
    • Condenser fan relay is stuck open.
    • Condenser fan motor malfunction
    • Condenser fan motor GND open
    • Open circuit between condenser fan motor and relay
    • Open circuit between condenser fan relay and PCM terminal 2C
    • Open battery power circuit for condenser fan relay
  • If main cooling fan motor does not operate, inspect for following: 
    • Main cooling fan relay is stuck open.
    • Main cooling fan motor malfunction
    • Main cooling fan motor GND open
    • Open circuit between cooling fan motor and relay
    • Open circuit between cooling fan relay and PCM terminal 2B
    • Open battery power circuit for cooing fan relay
5
  • Is drive belt okay?
 Yes Go to the next step.
No Replace drive belt.
6
  • Is there any leakage around heater unit in passenger compartment?
 Yes Inspect and service heater for leakage.
No Go to the next step.
7
  • Is there any leakage in coolant hoses and/or radiator?
 Yes Replace malfunctioning parts.
No Go to the next step.
8 Yes ECT and thermostat are okay, inspect engine block for leakage or blockage.
No Access ECT PID on WDS or equivalent.
Inspect for both ECT and temperature gauge readings.
  • If temperature gauge on instrument cluster indicates normal range but ECT is not same as temperature gauge reading, inspect ECT sensor.
  • If temperature gauge on instrument cluster indicates overheating but ECT is normal, inspect temperature gauge and heat gauge unit.
9
  • Verify test results.
    • If okay, return to diagnostic index to service any additional symptoms.
    • If malfunction remains, inspect related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis.
      • If vehicle is repaired, troubleshooting completed.
      • If vehicle is not repaired or additional diagnostic information is not available, replace PCM.
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.