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 < ...
Detected condition and possible cause
Detected condition
Possible cause
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Ecm does not receive communication signal from the ...
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