Suzuki GSX-R 1000 Service Manual: DTC “c23” (p1651-h/l): to sensor circuit
malfunction
Detected condition and possible cause
Detected condition |
Possible cause |
C23 |
The sensor voltage should be the
following for 2 sec. And more, after ignition
switch is turned on.
0.2 V ≤ Sensor voltage < 4.8 V |
- To sensor circuit open or short.
- To sensor malfunction.
- Ecm malfunction.
- To sensor circuit is open or ground circuit open
- To sensor circuit is open or shorted to ground or vcc
circuit open.
|
P1651 |
H |
Sensor voltage is higher than specified
value. |
L |
Sensor voltage is lower than specified
value. |
Wiring diagram

Troubleshooting
Caution
when using the multi-circuit tester, do not strongly touch the terminal
of the ecm coupler with a
needle pointed tester probe to prevent terminal damage. |
Note
after repairing the trouble, clear the dtc using sds tool. Refer to “use
of sds diagnosis reset procedures” . |
C23 (use of mode select switch)
Step |
Action |
Yes |
No |
1 |
- Turn the ignition switch off.
- Remove the front seat. Refer to “exterior parts removal and
installation” in section 9d .
- Remove the ap sensor from the bracket.
- Check the to sensor coupler (1) for loose or poor
contacts.
If ok, then measure the to sensor resistance.

- Remove the to sensor.
- Measure the resistance between terminal “a” and
terminal “c”.
Special tool
(a): 09900–25008 (multi
circuit tester set)
Tester knob indication
resistance (Ω)
To sensor resistance
16.5 – 22.3 KΩ
(terminal “a” – terminal “c”)

Is the resistance ok? |
Go to step 2. |
Replace the to sensor
with a new one. Refer to
“to sensor removal
and installation” in
section 1c (page 1c-
6). |
P1651-h (use of sds)
Step |
Action |
Yes |
No |
1 |
- Turn the ignition switch off.
- Remove the front seat. Refer to “exterior parts removal and
installation” in section 9d .
- Check the to sensor coupler (1) for loose or poor
contacts.
If ok, then check the to sensor lead wire continuity.

- Disconnect the to sensor coupler.
- Check the continuity between the r wire and b wire. If
the sound is not heard from the tester, the circuit
condition is ok.
Special tool
(a): 09900–25008 (multi
circuit tester set)
Tester knob indication
continuity test ( )

- Disconnect the ecm coupler. Refer to “ecm removal and
installation” in section 1c .
- Insert the needle pointed probes to the lead wire coupler
- Check the continuity between the b wire and terminal
“31”. Also, check the continuity between b/br wire and
terminal “35”.
Special tool
(a): 09900–25008 (multi
circuit tester set)
(b): 09900–25009
(needle-point probe set)
Tester knob indication
continuity test ( )
Ecm coupler (harness side)

Is the continuity ok? |
Go to step 2. |
B wire shorted to vcc,
or b/br wire open. |
P1651-l (use of sds)
Step |
Action |
Yes |
No |
1 |
- Turn the ignition switch off.
- Remove the front seat. Refer to “exterior parts removal and
installation” in section 9d .
- Check the to sensor coupler (1) for loose or poor
contacts.
If ok, then check the to sensor lead wire continuity.

- Disconnect the to sensor coupler.
- Check the continuity between the b wire and ground.
Also, check the continuity between the b wire and b/br
wire. If the sound is not heard from the tester, the circuit
condition is ok.
Special tool
(a): 09900–25008 (multi
circuit tester set)
Tester knob indication
continuity test ( 
)

- Disconnect the ecm coupler. Refer to “ecm removal and
installation” in section 1c .
- Insert the needle pointed probes to the lead wire coupler.
- Check the continuity between the r wire and terminal
“7”. Also, then check the continuity between b wire and
terminal “31”.
Special tool
(a): 09900–25008 (multi
circuit tester set)
(b): 09900–25009
(needle-point probe set)
Tester knob indication
continuity test (
 )
Ecm coupler (harness side)

Is the continuity ok? |
Go to step 2. |
R or b wire open, or b
wire shorted to ground. |
2 |
- Connect the ecm coupler and to sensor coupler.
- Insert the needle pointed probes to the lead wire coupler.
- Turn the ignition switch on.
- Measure the voltage at the wire side coupler between b
wire and b/br wire.
Special tool
(a): 09900–25008 (multi
circuit tester set)
(b): 09900–25009
(needle-point probe set)
Tester knob indication
voltage ( )
To sensor voltage (normal)
0.4 – 1.4 V
((+) terminal: b – (–) terminal: b/br)

- Dismount the to sensor from its bracket and measure
the voltage when it is leaned 65° and more, left and right,
from the horizontal level.
Special tool
(a): 09900–25008 (multi
circuit tester set)
(b): 09900–25009
(needle-point probe set)
To sensor voltage (leaning)
3.7 – 4.4 V
((+) terminal: b – (–) terminal: b/br)

Is the voltage ok? |
- R, b or b/br wire
open or shorted to
ground, or poor “7”,
“31” or “35”
connection.
- If wire and
connection are ok,
intermittent trouble or
faulty ecm.
- Recheck each
terminal and wire
harness for open
circuit and poor
connection.
- Replace the ecm with a known good one, and inspect it again.
Refer to “ecm removal and installation” in section 1c .
|
- Loosen or poor
contacts on the ecm
coupler.
- Open or short circuit.
- Replace the to sensor with a new one. Refer to “to sensor
removal and installation” in section 1c .
|
DTC “c24” (p0351), “c25” (p0352), “c26”
(p0353) or “c27” (p0354): ignition system
malfunction
Note
refer to “no spark or poor spark” in section 1h for details. |
Detected condition and possible cause
Detected condition
Possible cause
C22
Ap sensor voltage is not within the
following range.
0.5 V ≤ Sensor voltage < ...
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Detected condition
Possible cause
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Detected condition and possible cause
Detected condition
Possible cause
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Pair control solenoid valve circuit open or short.
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Side stand
An interlock switch is provided to
cut off the ignition circuit when the
side stand is down and the transmission
is in any gear other than
neutral.
The side stand/ignition interlock
switch works as follows:
if the side stand is down and
the transmission is in gear, the
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