Suzuki GSX-R 1000 Service Manual: DTC “c21” (p0110-h/l): iat sensor circuit malfunction

Detected condition

Possible cause

0.15 V ≤ Sensor voltage < 4.85 V

• Iat sensor circuit open or short.
•  Iat sensor malfunction.
•  Ecm malfunction.
• Iat sensor circuit open or ground circuit open.
• Iat sensor circuit shorted to ground.

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.

after repairing the trouble, clear the dtc using sds tool. Refer to “use of sds diagnosis reset procedures” .

Step

Action

Yes

No

1

1. Turn the ignition switch off.
2.  Lift and support the fuel tank. Refer to “fuel tank removal and installation” in section 1g .
3.  Move the air cleaner box upward. Refer to “air cleaner box removal and installation” in section 1d (page 1d- 7).
4.  Check the iat sensor coupler (1) for loose or poor contacts.

   If ok, then measure the iat sensor input voltage.

5. Disconnect the iat sensor coupler and turn the ignition switch on.
6.  Measure the input voltage between the dg wire terminal and ground.

   If ok, then measure the input voltage between the dg wire terminal and b/br wire terminal.

Special tool
(a): 09900–25008 (multi
circuit tester set)

Tester knob indication voltage ( )

Iat sensor input voltage 4.5 – 5.5 V ((+) terminal: dg – (–) terminal: ground, (+) terminal: dg – (–) terminal: b/br)

Is the voltage ok?

• Loose or poor contacts on the ecm coupler.
•  Open or short circuit in the dg or b/br wire.

Step

Action

Yes

No

1

1. Turn the ignition switch off.
2.  Lift and support the fuel tank. Refer to “fuel tank removal and installation” in section 1g .
3.  Move the air cleaner box upward. Refer to “air cleaner box removal and installation” in section 1d (page 1d- 7).
4.  Check the iat sensor coupler (1) for loose or poor contacts.

   If ok, then check the iat sensor lead wire continuity.

5. Disconnect the iat sensor coupler.
6.  Disconnect the ecm coupler. Refer to “ecm removal and installation” in section 1c .
7.  Insert the needle pointed probes to the lead wire coupler.
8.  Check the continuity between the dg wire and terminal “33”. Also, check the continuity between the 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 couplers (harness side)

Is the continuity ok?

Step

Action

Yes

No

1

1. Turn the ignition switch off.
2.  Lift and support the fuel tank. Refer to “fuel tank removal and installation” in section 1g .
3.  Move the air cleaner box upward. Refer to “air cleaner box removal and installation” in section 1d (page 1d- 7).
4.  Check the iat sensor coupler (1) for loose or poor contacts.

   If ok, then check the iat sensor lead wire continuity.

5. Disconnect the iat sensor coupler.
6.  Check the continuity between the dg wire and ground. 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 ( )

7. Connect the iat sensor coupler.
8.  Turn the ignition switch on.
9.  Insert the needle pointed probes to the lead wire coupler.
10. Measure the output voltage between the dg wire and ground.

Special tool
(a): 09900–25008 (multi
circuit tester set)
(b): 09900–25009
(needle-point probe set)

Tester knob indication voltage ( )

Iat sensor output voltage 0.15 – 4.85 V ((+) terminal: dg – (–) terminal: ground)

Are the continuity and voltage ok?

• Dg wire shorted to ground.
•  If wire is ok, go to step 2.

2

1. Turn the ignition switch off.
2.  Remove the air cleaner box. Refer to “air cleaner box removal and installation” in section 1d .
3.  Measure the iat sensor resistance.

Special tool
(a): 09900–25008 (multi
circuit tester set)

Tester knob indication resistance (Ω)

Iat sensor resistance approx. 2.58 KΩ at 20 °c (68 °f) (terminal – terminal)

Is the resistance ok?

• Dg or b/br wire open or shorted to ground, or poor “33” 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 .