Workshop Manual

7A–20
AUTOMATIC TRANSMISSION (4L30–E)
Chart 15a: Possible Causes of Low Line Pressure
Step
Action
Yes No
1 Check oil level.
Was the problem found?
Fill with ATF Go to Step 2
2 Check for defective throttle position sensor.
Was the problem found?
Replace throttle
position sensor
Go to Step 3
3 Check for plugged, loose, or damaged oil filter (79).
Was the problem found?
Inspect oil filter,
tighten bolts or
replace oil filter
(79)
Go to Step 4
4 Check for a stuck force motor plunger (404). (Adapter case valve
body)
Was the problem found?
Replace force
motor plunger
(404)
Go to Step 5
5 Check for a stuck feed limit valve (412). (Adapter case valve body)
Was the problem found?
Replace feed limit
valve (412)
Go to Step 6
6 Check for loose converter bolts (4 & 5).
Was the problem found?
Tighten converter
bolts (4 & 5)
Go to Step 7
7 Check for a stuck pressure regulator valve (217). (Oil pump)
Was the problem found?
Replace pressure
regulator valve
(217)
Go to Step 8
8 Check for a stuck boost valve (213).(Oil pump)
Was the problem found?
Replace boost
valve (213)
Go to Step 9
9 Check for blocked intermediate oil passages to pressure
regulator valve. (Oil pump)
Was the problem found?
Replace oil pump Go to Step 10
10 Check for defective oil pump (9, 201, 202 & 228).
Was the problem found?
Replace oil pump Go to Step 11
11 Check for internal leaks.
– Check balls missing or out of location in valve bodies
– Seals cut or damaged
– Gaskets defective, etc.
Was the problem found?
Install balls, or
correct ball
location
Replace seals
Replace gaskets
—