Checking Partial Throttle Enrichment; Checking Pressure Switch; Checking Speed Switch - BMW 745i Repair Instructions

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Anschlul3- Schema
zu Klemme 31
zu Klemme 15
ZU' Klemme15
zum TSZ-Steuergerat KI 16
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Checking Partial Throttle Enrichment
Connect BMW service test unit or BMW digital test er
and CO tester .
Detach hose on pressure switch.
Start engine.
While engine speed is picking up CO level should
be 5.7 ... 7 % by volume at a speed of 4150 .!. 150
rpm .
While engine speed is tailing off CO level should
drop at a speed of 3900.±. 150 , r pm .
SEPARATE TESTS:
a) Checking Pressure Switch
Pull off plug (1) .
Connect ohmmeter between both terminals.
Start engine.
Reading:
00
ohms.
Detach hose on pressure switch.
Reading:
<
0.08 ohms.
b) Check ing Speed Switch
Connect t achometer .
Connect voltmeter between ground and term. 1 on
speed switch .
Start engine.
There should be voltage from engine speed of 4150
.±. 150 rpm.
Troubleshooting hints:
Voltage at term. 2 and 5?
Speed signal at term. 4?
If yes, replace speed switch .
Checking with BMW service test unit:
Perform test step Mot 01, Mot 02.
1 to Pressure switch
2 to Terminal 15
3 to Terminal 31
4 to Control Unit for Transistorised Ignition
Terminal 16
5 to Terminal 15
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