Mazda MX-6 1998, Workshop Manual

Page: 631 / 1282

TROUBLESHOOTING
DTC U2021 Engine control system
DESCRIPTION
Torque reduction (engine condition) signal is normal, and received that signal indicates that PCM cannot
excute torque reduction
POSSIBLE
CAUSE
• Malfunction of engine control system
STEP INSPECTION
ACTION
— — —
Perform engine on-board diagnostic inspection,
e r 01-01B ENGINE ON-BOARD DIAGNOSIS
ANTILOCK BRAKE SYSTEM AND TRACTION CONTROL SYSTEM SYMPTOM TROUBLESHOOTING
W 6 U 4 0 1 W 0 5
Diagnostic Index
• Use the following table to determine the problem and go to the appropriate “Symptom Troubleshooting."
(F o r A B S
No. TROUBLESHOOTING ITEM
D E S C R IP T IO N
1 When IG switch is turned to
O N ,
ABS warning light does
not illuminate within 2— 4 seconds.
• Burnt out bulb, or short/open in harness
• Malfunction in instrument cluster (print board)
• Malfunction in ABS CM
Note
• After IG is turned to
O N ,
it is normal for the ABS
warning light to illuminate within 2— 4 seconds.
2 When IG switch is turned to
O N ,
ABS warning light
illuminates after more than 2— 4 seconds.
• Malfunction in ABS system
• Low battery voltage
• Ignition switch malfunction
• Generator malfunction
• Improper drive belt tension
• Poor connection in ABS CM harness
• Malfunction of ABS warning light harness
• Malfunction of instrument cluster (print board)
• ABS CM inoperative
3
When IG switch is turned to
O N ,
ABS warning light goes
on and off intermittently.
• Low battery voltage
• Poor ABS CM ground
• Malfunction of ABS warning light harness
• Malfunction of instrument cluster (print board)
• Improper bulb installation
• Poor connection in ABS harness connector
• Malfunction in ABS CM
4 ABS warning light illuminates normally, but system has
problem.
• Spongy brake feeling
• Poor braking
• Brakes pull to one side
• Brake pedal and brake master cylinder attachment
incorrect
• Air in brake system
• Malfunction of master cylinder
• Malfunction of proportioning valve
• Leakage of brake fluid
For ABS/TCS)
No.
TROUBLESHOOTING ITEM
DESCRIPTION
5 When IG switch is turned to ON, all following lights
illuminate improperly:
• ABS warning light
• TCS indicator light
• TCS OFF light
• Malfunction in ABS wiring system
• Malfunction of ABS/TCS CM
6
When IG switch is turned to ON, both following lights
illuminate improperly:
• TCS
indicator light
• TCS OFF light
• Malfunction of ABS/TCS CM or PCM
• Malfunction of harness on TCS indicator light or TCS
OFF light
• Communication error between TCS CM and PCM
• Malfunction of engine control system
0 4 -0 1 -1 2