NO.27 CONSTANT VOLTAGE[AJ (3.0L Duratec)]

id0103a7804300

27
Constant voltage
DESCRIPTION
•  Incorrect constant voltage
POSSIBLE CAUSE
•  Constant voltage circuit malfunction
Note
•  TP sensor and D.P.F. EGR sensor use constant voltage.

Diagnostic procedure

STEP

INSPECTION

RESULTS

ACTION
1
•  Disconnect the appropriate sensor connector when constant voltage circuit inspection failed.
•  Turn the ignition switch to the ON position (Engine off).
•  Measure the voltage between following appropriate sensor connector terminals:
―  Constant voltage terminal and ground terminal
•  Is the constant voltage above 6.0 V?
Yes
Go to Step 13.
No
Go to the next step.
2
•  Is the voltage across battery terminals above 10.5 V?
Yes
Go to the next step.
No
Inspect the charging system.
3
•  Turn the engine switch to the off position.
•  Leave appropriate sensor connector disconnected.
•  Measure the voltage between battery positive terminal and ground (between PCM and appropriate sensor) circuit at appropriate sensor connector.
•  Is the voltage above 10.5 V and within 1.0 V of battery voltage?
Yes
Go to the next step.
No
Go to Step 8.
4
Note
•  Purpose of this step is to determine if M-MDS is communicating with PCM.
•  Turn the ignition switch to the ON position (Engine off).
•  Attempt to access ECT PID.
•  Can ECT PID be accessed?
Yes
Go to Step 7.
No
Go to the next step.
5
•  Turn the engine switch to the off position.
•  Disconnect the TP sensor, D.P.F. EGR sensor and PCM connectors.
•  Turn the ignition switch to the ON position (Engine off).
•  Measure the voltage between following PCM connector terminals.
―  71/97 and 24/51/76/103
•  Is the voltage above 10.5 V?
Yes
Go to the next step.
No
Repair open circuit between the PCM terminal 71 and/or 97 and main relay.
6
•  Leave TP sensor, D.P.F. EGR sensor and PCM connectors disconnected.
•  Measure the resistance between PCM connector terminals.
―  90 and 24/51/76/103
•  Is the resistance above 10 kilohms?
Yes
Inspect for constant voltage at suspect sensor connector again.
No
Repair constant voltage circuit shorted to ground.
7
•  Turn ignition switch off.
•  Leave TP sensor disconnected.
•  Disconnect the PCM connector.
•  Measure the resistance between PCM connector terminal 90 and constant voltage circuit at appropriate sensor connector.
•  Is the resistance below 5.0 ohms?
Yes
Inspect for constant voltage at suspect sensor connector again.
No
Repair open constant voltage circuit.
8
Note
•  Purpose of this step is to determine if M-MDS is communicating with PCM.
•  Reconnect TP sensor connector.
•  Turn ignition switch on.
•  Attempt to access ECT PID.
•  Can ECT PID be accessed?
Yes
Go to the next step.
No
Go to Step 11.
9
•  Are DTCs present for two or more sensors connected to PCM terminal 91?
•  Sensor connected to PCM terminal 91:
―  ECT sensor (P0117, P0118, P0125)
―  HO2S (front) (P0131, P0132, P0151, P0152)
―  HO2S (rear) (P0138, P0158)
―  IAT sensor (P0112, P0113)
―  TP sensor (P0121, P0122, P0123)
Yes
Go to the next step.
No
Repair open ground circuit to sensor where constant voltage circuit inspection failed.
10
•  Turn the engine switch to the off position.
•  Disconnect the M-MDS from the DLC–2.
•  Disconnect the PCM connector.
•  Measure the resistance between ground circuit at appropriate sensor connector and PCM connector terminal 91.
•  Is the resistance below 5.0 ohms?
Yes
Reconnect sensor connector.
Go to the appropriate DTC test.
No
Repair open ground circuit.
11
•  Turn the engine switch to the off position.
•  Disconnect the PCM connector.
•  Measure the resistance between battery negative terminal and following PCM terminals.
―  3/24/51/76/103
•  Is the each resistance below 5.0 ohms?
Yes
Go to the next step.
No
Repair open ground circuit.
12
•  Turn the engine switch to the off position.
•  Measure the resistance between ground circuit at following sensor connector and ground:
―  TP sensor
―  D.P.F. EGR sensor
―  ECT sensor
―  IAT sensor
―  HO2S (front)
―  HO2S (rear)
•  Is the each resistance below 5.0 ohms?
Yes
Ground circuits are normal.
Inspect for constant voltage at suspect sensor connector again.
No
Inspect for open ground circuit.
13
•  Turn the engine switch to the off position.
•  Disconnect the TP sensor, D.P.F. EGR sensor, and PCM connectors.
•  Turn the ignition switch to the ON position (Engine off).
•  Measure the voltage between constant voltage circuit at TP sensor connector and battery negative terminal.
•  Is the voltage below 0.5 V?
Yes
Inspect for constant voltage at suspect sensor connector again.
No
Repair constant voltage circuit shorted to power in wiring harness.
14
•  Verify the test results.
―  If normal, return to the diagnostic index to service any additional symptoms.
―  If malfunction remains, inspect related Service Information and perform repair or diagnosis.
•  If vehicle is repaired, troubleshooting completed.
•  If vehicle is not repaired or additional diagnostic information is not available, replace the PCM.