Generac Power Systems GP Series Diagnostic Repair Manual page 57

Connect one meter test lead to terminal C of the
6.
sensor and connect the other meter test lead to
terminal D.
Start engine.
7.
Once engine is running and stabilized, the
8.
generator to greater than 25% of the generators
load.
With the generator running under load, measure
9.
and record the DC voltage indicated by the DMM.
a. If the DMM indicated a DC voltage between 0.3–
0.9 VDC, proceed to Step 11.
NOTE: The voltage may be steady or fluctuating.
b. If the DMM did not indicate a steady or fluctuating
DC voltage between 0.3–0.9 VDC, replace oxygen
sensor.
NOTE: Only a short time window exists to test the wiring
harness (approximately two minutes after the engine
shuts off).
Stop engine.
10.
Locate and disconnect
11.
connector from the harness.
Set a DMM to measure resistance.
12.
Connect one meter test lead to Wire 820G and the
13.
other meter test lead to Wire 805. Measure and
record the resistance.
NOTE: This step is measuring the resistance of the
sensor itself. With the engine shut down resistance will
start low (approximately 20 Ohms) and rise to an
INFINITE value. A rising resistance indicates the wire
integrity is good.
a. If the DMM did not indicate the proper resistance,
repair or replace wiring between the controller.
Test 34 – Troubleshooting Electronic
Throttle Control Valve (ETC)
5-3, 5-4, 5-5, 5-6)
The electronic throttle control valve (ETC) is a stepper
motor controlled throttle valve with a built in throttle
position feedback sensor. A 4-wire harness connects the
ETC to the ECM for throttle control and throttle position
feedback.
The sensor has a dedicated ground Wire 820G and a
dedicated power supply Wire 820B (4.5–5 VDC). Wire
766 is the sensor output to the ECM (4.5 VDC wide open
throttle, 0.5 VDC throttle fully closed).
Wire 770 is ETC positive (+), and Wire 771 is ETC
negative (–), with a motor resistance of 1.5 ohms. This
resistance is measured at the motor drive terminals
located inside the cover of the ETC valve. Resistance will
be higher (15–35 ohms) if measured on the external
cover.
Diagnostic Repair Manual
the oxygen sensor
(Fault codes
Section 5 Engine Diagnostic Tests
ETC
A:ORANGE
B:YELLOW
C:PINK
D:BLUE
Figure 5-99. Electronic Throttle Control Valve (ETC)
NOTE: Needle probes are not recommended for the type
of connector used on the ETC valve harness. If the
control panel generates any ETC codes, Operate the
throttle plate manually with a non-metallic probe to check
for smooth movement. Replace the ETC valve if
necessary.
Problems With Loading and Overspeed
Shutdown
If a unit is having a hard time with loading (frequency dips
excessive or response time is poor) or when going from a
heavy load to a low or no load and the unit overspeeds
and shuts down, there may be a problem with the ECM
current transformer (CT1).
CT1 is installed on one of the alternator output power
leads. CT1 detects large load swings that are being
applied to the unit. As these load swings hit the unit, the
ECM will temporarily modify the emission characteristics
for better load response.
CONN1P-11 398A
CONN1P-12 399A
Figure 5-100. Current Transformer (CT1)
770A ECM-1H
771A ECM-1G
770B ECM-1F
771B ECM-1E
015051
FROM ALTERNATOR
AØ BØ N
CT1
+
RED
BLK
-
L1 L2 N
TO CONTROL PANEL
015622
51