
80 RENR5622
Troubleshooting Section
Test Step 5. Check the Coolant Flow
Switch
Pressurized System: Hot coolant can cause seri-
ous burns. To open the cooling system filler cap,
stop the engine and wait until the cooling system
components are cool. Loosen the cooling system
pressure cap slowly in order to relieve the pres-
sure.
A. Drain the engine coolant below the coolant flow
switch.
B. Remove the coolant flow switch from the engine.
C. Manually close the coolant flow switch. Ensure
that excessive force is not required to close the
switch.
D. Measure continuity between termnal 1 and
terminal 2 with the switch in the closed position.
Expected Result:
The switch closes easily and there is continuity
between terminal 1 and terminal 2 with the switch in
theclosedposition.
Results:
•
OK – There may be a mechanical problem with
the engine’s cooling system.
Repair: Refer to Systems Operation/Testing and
Adjustingforinformationontestingthecooling
system.
Verify that the repair eliminates the problem.
STOP.
•
Not OK – There is a problem with the coolant flow
switch.
Repair: Replace the coolant flow switch with a
new switch.
Verify that the repair eliminates the problem.
STOP.
Test Step 6. Check the ECM
A. Disconnect the J1/P1 ECM connector.
B. Remove wire 412-BU from ECM connector P1-30.
Install a wire with Deutsch sockets on each end
into P1-30.
C. Reconnect the J1/P1 ECM connector.
D. Use a suitable piece of wire to short the wire
jumperinP1-30toengineground.
E. Turn the keyswitch to the ON position.
F. Observe the st
atus of “Engine Coolant Flow” on
Cat ET.
G. Turn the keysw
itch to the OFF position.
Expected Result:
The status indicates “Flow” with the jumper wire in
place.
Results:
•
OK – The status
indicates “Flow” with the jumper
wire in place.
Repair: Ther
eisanopeninthewirebetween
termnal 1 and the ECM and/or there is an open
in the digital return wire between termnal 2 and
P2-54. Repai
rthewire.
STOP.
•
Not OK – The status indicates “NO FLOW”. The
ECM is not responding correctly.
Repair: Verify your results.
Refer to Trou
bleshooting, “Replacing the ECM”
before replacing the ECM.
Verify that
the repair eliminates the problem.
STOP.
i02409465
Electrical P ower Sup ply
SMCS Code: 1401-038
System Oper
ation Description:
Use this procedure to troubleshoot the electrical
system if a p
roblem is suspected with the power to
the engine’s Electronic Control Module (ECM) or if
any one of the diagnostic codes or the event code in
Table28is
active or easily repeated.