LEXUS SC400 1991 Service Repair Manual

LOCATION OF CONNECTORS
Location of Connectors in Engine Compartment
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ENGINE TROUBLESHOOTING Location of Connectors
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Location of Connectors in Instrument Panel
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Location of Connectors in Instrument Panel (Cont'd)
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Location of Connectors in Body
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CIRCUIT INSPECTIONDiag. Code 12
RPM Signal Circuit (No. 1)
CIRCUIT DESCRIPTION
The distributor in the Engine Control System contains three pick±up coil\
s (G1, G2 and NE).
The G1, G2 signals inform the ECU of the standard crankshaft angle.
The NE signals inform the ECU of the crankshaft angle and the engine spe\
ed.
 Code No. Diagnostic Code Detecting Condition Trouble Area
  
NoºNEºorºG1ºandºG2ºsignal to ECU within 2
 

Open or short in NE G circuit  No ºNEº or ºG1º and ºG2º signal to ECU within 2
sec after cranking 
Open or short in NE, G circuit.

Distributor
 12 sec. after cranking. 
Distributor

Open or short in STA circuit.
ECU  Open in ºGº
circuit. 
Oen or short in STA circuit.

ECU
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DIAGNOSTIC CHART
WIRING DIAGRAM
Check resistance of each pickup coils in
distributor
Check for open and short in harness and
connector between ECU and distributor.
Check air gap.
Check and replace ECU.
Replace distributor.
Repair or rep lace harness or connector.
Replace distributor
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Disconnect distributor connector.
Measure resistance between each terminal shown in
table below.
Check resistance of each picup coils in distributor.

During cranking or idling, check between terminals G1,
G2, NE and G
of engine (&ECT) ECU.
HINT: The correct waveforms appears as shown in the illustration on the left.
Replace distributor.
Check for open and short in harness and connector between engine
(&ECT) ECU and distributor (See page IN±27
Repair or replace harness or connector.
INSPECTION PROCEDURE
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Remove distributor cap & rotor.
Using SST (G1 and G2 pickups) and a thikness gauge
(NE pickup). measure the air gap between the signal
rotor projection and pickup coil.
SST 09240±00020 fro G1 and G2 pickups
Air gap: 0.2±0.4 mm (0.008±0.016 in.)
Replace distributor.
Check and replace engine (& ECT) ECU.
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