Isuzu KB P190. 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