Isuzu KB P190. Service manual — part 1090
7A2-76 TRANSMISSION CONTROL SYSTEM (JR405E)
4
Place the selector lever in R range while observing
the Low & Reverse Brake Pressure Switch
parameter with a scan tool.
Does the Low & Reverse Brake Pressure Switch
parameter indicate ON?
—
Go to Diagnostic
Aids
Go to Step 5
5
1.
Turn OFF the ignition.
2.
Disconnect the in-line harness connector (E-
54) near the transmission range switch.
3.
Turn ON the ignition, with the engine OFF.
4.
Observe the Low & Reverse Brake Switch
parameter with a scan tool while momentarily
jumping 3-amp fused jumper wire between pin
12 of E-54 (female side) and a known good
ground.
Does the scan tool indicate ON when the circuit is
jumpered and OFF when the circuit is not
jumpered?
—
Go to Step 8
Go to Step 6
6
1.
Test the signal circuit between the TCM (pin
12 of C-95) and the in-line harness connector
(pin 12 of E-54 female side) for the following
conditions:
• An open circuit
• A short to ground
• High resistance
2.
Repair the circuit(s) as necessary.
Did you find and correct the condition?
—
Go to Step 13
Go to Step 7
7
1.
Turn OFF the ignition.
2.
Disconnect the TCM harness connector.
3.
Inspect for an intermittent and for a poor
connection at the harness connector of the
TCM (pin 12 of C-95).
4.
Repair the connection(s) as necessary.
Did you find and correct the condition?
—
Go to Step 13
Go to Step 12
8
1.
Inspect for an intermittent and for a poor
connection at the in-line harness connector
(pin 12 of E-54).
2.
Repair the connection(s) as necessary.
Did you find and correct the condition?
—
Go to Step 13
Go to Step 9
Step
Action
Value(s)
Yes
No
TRANSMISSION CONTROL SYSTEM (JR405E) 7A2-77
9
1.
Remove the transmission oil pan. Refer to
repair instructions (On-Vehicle Service).
2.
Inspect the low & reverse brake solenoid valve
and transmission fluid pressure (TFP) switch
for the following conditions:
• Physical damage
• Loose or improper installation
3.
Inspect for an intermittent and for a poor
connection at the harness connector of the
low & reverse brake TFP switch or in-line
harness connector.
4.
Test the signal circuit between the low &
reverse brake TFP switch and the in-line
harness connector (pin 12 of E-54 male side)
for the following conditions:
• An open circuit
• A short to ground
• A short to the solenoid valve circuit
• High resistance
5.
Repair the connection(s), circuit(s) or replace
as necessary.
Did you find and correct the condition?
—
Go to Step 13
Go to Step 10
10
1.
Remove the low & reverse brake solenoid
valve and TFP switch from the valve body
assembly and perform function check. Refer
to repair instructions (On-Vehicle Service).
2.
Repair or replace as necessary.
Did you find and correct the condition?
—
Go to Step 13
Go to Step 11
11
Repair or replace the valve body assembly. Refer
to repair instructions (On-Vehicle Service or Unit
Repair).
Did you complete the repair or replacement?
—
Go to Step 13
—
12
Important: Replacement TCM must be
programmed.
Replace the TCM. Refer to TCM Replacement.
Did you complete the replacement?
—
Go to Step 13
—
13
1.
Reconnect all previously disconnected
components or harness connector(s).
2.
Clear the DTCs with a scan tool.
3.
Turn OFF the ignition for 30 seconds.
4.
Start the engine.
5.
Drive the vehicle while observing the DTC
Information with a scan tool.
Did the DTC fail this ignition?
—
Go to Step 2
Go to Step 14
14
Observe the DTC Information with a scan tool.
Are there any DTCs that you have not diagnosed?
—
Go to DTC List
System OK
Step
Action
Value(s)
Yes
No
7A2-78 TRANSMISSION CONTROL SYSTEM (JR405E)
DTC P1858 (Flash Code 27)
Circuit Description
The 2-4 brake transmission fluid pressure (TFP) switch
is installed to the lower part of the valve body assembly
and it feedbacks fluid pressure in the 2-4 brake
hydraulic circuit. When the solenoid valve is energized,
fluid pressure is drained to disengage the 2-4 brake
and the TFP switch is OFF. When the solenoid valve is
not energized, fluid pressure is applied to engage the
2-4 brake and the TFP switch is ON. The TCM
monitors the 2-4 brake pressure switch ON/ OFF status
through the signal circuit. If the TCM detects an
improper status on the signal circuit, this DTC will set.
Condition for Running the DTC
• DTCs P0560, P0705, P0717, P0722, P0753,
P0758, P0763, P0768, P1120, P1750, P1755 and
P1875 are not set.
AND following conditions are met for longer than 2.5
seconds.
• The ignition switch is ON.
• The transmission fluid temperature is more than
60
°C (140°F).
• The engine speed is more than 500 RPM.
• The TCM is not under gearshift control.
Condition for Setting the DTC
Either of following condition is met:
• The TCM detects that the 2-4 brake TFP switch
signal is stuck at the ON for longer than 2 seconds
when the selector lever in P, R or N range.
• The TCM detects that the 2-4 brake TFP switch
signal is stuck at the OFF for longer than 2 second
when the selector lever in D range with 4th gear.
Action Taken When the DTC Sets
• The TCM blinks the Check Trans lamp when the
diagnostic runs and fails.
Condition for Clearing the DTC
• The TCM turns OFF the Check Trans lamp when
the diagnostic runs and does not fail.
• A current DTC clears when the diagnostic runs and
does not fail.
Diagnostic Aids
• If an intermittent condition is suspected, refer to
Intermittent Conditions in this section.
• Use the Clutch, Brake, Solenoid and Pressure
Switch Logic table to verify each component works
properly within the selected gear range.
• A sticking or intermittently sticking the 2-4 brake
solenoid valve will cause this DTC to set.
Schematic Reference: Transmission Controls
Schematics
Connector End View Reference: Transmission
Controls Connector End Views or TCM Connector End
Views
Circuit/ System Testing DTC P1858
Step
Action
Value(s)
Yes
No
1
Did you perform the Diagnostic System Check -
Transmission Controls?
—
Go to Step 2
Go to Diagnostic
System Check -
Transmission
Controls
2
1.
Install a scan tool.
2.
Turn OFF the ignition for 30 seconds.
3.
Lift the driving wheels or drive the vehicle
while observing the DTC Information with a
scan tool.
Is DTC P0758 also set?
—
Go to DTC P0758
Go to Step 3
3
Place the selector lever in forward range while
observing the 2-4 Brake Pressure Switch
parameter with a scan tool.
Does the 2-4 Brake Pressure Switch parameter
ever indicate OFF when gear is positioned 2nd and
4th?
—
Go to Step 5
Go to Step 4
TRANSMISSION CONTROL SYSTEM (JR405E) 7A2-79
4
Place the selector lever in P, R and N range while
observing the 2-4 Brake Pressure Switch
parameter with a scan tool.
Does the 2-4 Brake Pressure Switch parameter
indicate OFF?
—
Go to Diagnostic
Aids
Go to Step 5
5
1.
Turn OFF the ignition.
2.
Disconnect the in-line harness connector (E-
54) near the transmission range switch.
3.
Turn ON the ignition, with the engine OFF.
4.
Observe the 2-4 Brake Switch parameter with
a scan tool while momentarily jumping 3-amp
fused jumper wire between pin 7 of E-54
(female side) and a known good ground.
Does the scan tool indicate ON when the circuit is
jumpered and OFF when the circuit is not
jumpered?
—
Go to Step 8
Go to Step 6
6
1.
Test the signal circuit between the TCM (pin 1
of C-95) and the in-line harness connector (pin
7 of E-54 female side) for the following
conditions:
• An open circuit
• A short to ground
• High resistance
2.
Repair the circuit(s) as necessary.
Did you find and correct the condition?
—
Go to Step 13
Go to Step 7
7
1.
Turn OFF the ignition.
2.
Disconnect the TCM harness connector.
3.
Inspect for an intermittent and for a poor
connection at the harness connector of the
TCM (pin 1 of C-95).
4.
Repair the connection(s) as necessary.
Did you find and correct the condition?
—
Go to Step 13
Go to Step 12
8
1.
Inspect for an intermittent and for a poor
connection at the in-line harness connector
(pin 7 of E-54).
2.
Repair the connection(s) as necessary.
Did you find and correct the condition?
—
Go to Step 13
Go to Step 9
Step
Action
Value(s)
Yes
No
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