Test 2: Tachometer Output (CTO) Failure
TEST 2: TACHOMETER OUTPUT (CTO) FAILURE
| TEST 2 |
TACHOMETER OUTPUT (CTO) FAILURE |
| STEP |
INSPECTION |
ACTION |
| 1 |
CHECK CTO CIRCUIT FOR SHORT TO POWER
- Install Breakout Box, leave PCM disconnected.
- Key ON.
- Engine OFF (KOEO).
- Measure voltage of CTO circuit between test pin 48 at Breakout Box and ground.
- Key OFF.
- Is voltage less than 0.5 volt?
|
Yes |
Go to step 2. |
| No |
Repair short circuit.
Verify symptom no longer exists. |
| 2 |
CHECK CTO CIRCUIT FOR SHORT TO GROUND IN HARNESS
- Disconnect PCM.
- Disconnect 16-pin instrument cluster connector C-214.
- Measure resistance between test pin 48 (CTO SIG) and test pins 51, 76, 77 or 103 (PWR GND) and chassis ground.
- Measure resistance between test pin 48 (CTO SIG) and chassis ground.
- Are both resistances greater than 10, 000 ohms?
|
Yes |
Go to step 3. |
| No |
Repair short in harness.
Verify a symptom no longer exists. |
| 3 |
CHECK CTO CIRCUIT FOR OPEN HARNESS
- Measure the resistance of CTO circuit (T/Y) between test pin 48 at Breakout Box and pin 15 of 16-pin instrument cluster connector C-214.
- Is the resistance less than 5.0 ohms?
|
Yes |
Go to step 4. |
| No |
Repair open circuit.
Verify symptom no longer exists. |
| 4 |
CHECK CTO SIGNAL FROM PCM
- Connect PCM.
- Key ON, Engine Running (KOER).
- Measure voltage of CTO circuit (T/Y) between pin 15 of 16-pin instrument cluster connector C-214 and ground.
- Is voltage reading between 3.0 and 9.0 volts?
|
Yes |
|
| No |
Open or short in PCM.
Replace PCM. See COMPUTERIZED ENGINE CONTROLS
.
Verify symptom no longer exists. |