Isuzu N-Series. Manual - part 925
Transmission Control System (Smoother) 7A-155
P1901 (Flash Code 19)
Circuit Description
The half-clutch adjustment switch is used to adjust the
clutch engagement timing. The clutch engages too fast/
slow when starting vehicle or the clutch engagement
timing does not match with the driver preference when
starting vehicle, the driver can select the timing by
pressing either “FAST” or “SLOW” adjustment switch. If
the TCM detects the half-clutch adjustment fast switch
signal continuously “ON”, this DTC will set.
Condition for Running the DTC
• The ignition switch is ON.
• The ignition voltage is more than 20 volts.
• The emergency switch is OFF.
• The vehicle speed is more than 5 km/h (3 MPH)
Condition for Setting the DTC
• The TCM detects that the half-clutch adjustment
fast switch signal is stuck at the ON position (high
voltage).
Action Taken When the DTC Sets
• The TCM does not illuminate the transmission
warning lamp when the diagnostic runs and fails.
• The TCM inhibits half-clutch adjustment.
Condition for Clearing the DTC
• A current DTC clears when the diagnostic runs and
does not fail.
• A history 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.
DTC P1901 (Flash Code 19)
Schematic Reference: Transmission Controls
Schematics
Connector End View Reference: Transmission
Controls Connector End Views or Transmission Control
Module (TCM) Connector End Views
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 the Tech 2.
2. Turn ON the ignition, with the engine OFF.
3. Observe the Fast Switch parameter with the
Tech 2.
Does the Fast Switch parameter indicate OFF?
—
Go to Diagnostic
Aids
Go to Step 3
3
1. Turn OFF the ignition.
2. Disconnect the half-clutch adjustment switch
harness connector.
3. Turn ON the ignition, with the engine OFF.
4. Observe the Fast Switch parameter with the
Tech 2.
Does the Fast Switch parameter indicate OFF?
—
Go to Step 5
Go to Step 4
4
1. Test the half-clutch adjustment switch circuit
between the transmission control module
(TCM) (pin 2 of B-428 connector) and the half-
clutch adjustment switch (pin 1 of B-106
connector) for a short to battery or ignition
voltage.
2. Repair the circuit(s) as necessary.
Did you find and correct the condition?
—
Go to Step 7
Go to Step 6
5
Replace the half-clutch adjustment switch.
Did you complete the replacement?
—
Go to Step 7
—
6
Important:
Replacement TCM must be programmed and
learned.
Replace the TCM. Refer to Transmission Control
Module (TCM) Replacement in this section.
Did you complete the replacement?
—
Go to Step 7
—