Page 690 - Workshop Manual - Tunland (2017)

04-4 DIAGNOSTICS - ENGINE CONTROL SYSTEM

04
WARNING

• Use special-purpose check lines instead of ordinary test bars to measure the
resistance and conduction between the terminals, so as not to affect the contact
pressure of terminals.
• It is unnecessary to conduct checks as per the sequence listed in the check list.
• To check the resistance and conduction between the terminals, incorrect terminal
insertion or incorrect short-circuit groundinggrounding (ground) of connector
terminals may possibly damage the vehicle-body harness, sensors, ECM or
multimeter, be careful!
• If the tested results are different from the standard value, check relevant sensors,
actuators and harness, and repair or replace them when necessary.
• When repair or replacement is finished, check the values over again, and verify
whether or not the failure is eliminated.

(n) Grounding (ground) checks
• Remove the grounding bolt or screw.
• Check all mating surfaces for blemish, soil and rust etc.

• Clean them as necessary so as to ensure good contact.
• Remount the bolts or screws securely.
• Check for any "additional" accessories that may interfere with the grounding
circuit.
• If multiple conductors are press-bonded to 1 grounding hole, check it for correct
press bond. Verify that all circuits are cleaned, secured and earthed properly.
If multiple strands of electric wires are fitted to 1 grounding hole, verify that there
is no grounding (earth) wire with too long insulating sheath.
• To replace the ECM, conduct adequate diagnosis of other causes since ECM
is an expensive product with high reliability and cannot be damaged in most
cases.

WARNING

• Grounding connection is extremely important for normal operation of the electric
and electronic circuits.The grounding connection is usually exposed to moisture,
soil and other corrosive chemicals. Additional resistance may be generated in
the eroded (rusted) places.The said additional resistance may change the
working properties of the circuits.
• The electronic control circuits are extremely sensitive to the correctness of
grounding, and loose or corroded grounding may have a strong impact on the
electronic control circuits. Poor grounding or corrosion may easily affect the
circuits.The earthed place may be covered by a layer of thin rust even though
it appeared clean.