Circuit Description
The Crankshaft Position (CKP) sensor sends a reference signal to the Vehicle Control Module (VCM). The CKP reference signal is used to determine crankshaft position and engine RPM. This information is used by the VCM in order to determine when to pulse the ignition coil and to control the ignition timing. This diagnostic will detect a low duty cycle from the crankshaft sensor. This is a type B DTC.
Conditions for Setting the DTC
| • | The engine speed is less than 4000 RPM. |
| • | The MAF is at least 5 g/s. |
| • | The crank sensor duty cycle High Reference to Low Reference ratio is greater than 0.6875. |
Action Taken When the DTC Sets
The VCM stores the DTC in History if the VCM detects an intermittent problem.
Conditions for Clearing the MIL/DTC
A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (the coolant temperature has risen 40°F from the start-up coolant temperature and the engine coolant temperature exceeds 160°F during that same ignition cycle) or the scan tool clearing feature has been used.
Diagnostic Aids
A poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation may cause an intermittent.
Throroughly check any circuitry that is suspected of causing the intermittent complaint. Check for the following conditions:
| • | Backed out terminals |
| • | Improper mating |
| • | Broken locks |
| • | Improperly formed or damaged terminals |
| • | Poor terminal to wiring connections or |
| • | Physical damage to the wiring harness |
Refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step determines if DTC P0338 is the result of a hard failure or an intermittent condition.
-
Determines if voltage is available to the CKP through the VCM.
-
If the feed circuit is shorted to ground, the test light will be ON. This step determines if the circuit is open or shorted to ground. If the circuit is OK, then the VCM connections or VCM is faulty.
-
This test checks the crank sensor, crank sensor signal circuit and the VCM.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Important: Before clearing the DTCs, use the scan tool to record the Freeze Frame and the Failure Records for reference. This data will be lost when the Clear Info function is used. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
2 | Does the engine start? | -- | ||
Clear DTCs crank the engine for 10 seconds. Does DTC P0338 set? | -- | |||
4 | Start the engine, observe the engine RPM on the scan tool. Does the RPM fluctuate (up to twice desired RPM)? | -- | ||
Is the test lamp on? | -- | |||
Jumper the test lamp between cavities B and C of the Crankshaft Position sensor electrical connector. Is the test lamp on? | ||||
Is the voltage between the specified value? | 2-3V | |||
8 |
Is the test lamp off? | -- | ||
9 | Check the Crankshaft Position sensor signal circuit for an open. Was a problem found? | -- | ||
10 | Check the Crankshaft Position sensor signal circuit for a short to ground. Was a problem found? | -- | ||
11 | Repair short to ground in Crankshaft Position sensor feed circuit. Refer to Wiring Repairs in Engine Electrical. Is the repair complete? | -- | -- | |
12 | Repair the open in the Crankshaft Position sensor ground circuit. Refer to Wiring Repairs in Engine Electrical. Is the action complete? | -- | -- | |
13 | Check for a faulty connection at the Crankshaft Position sensor. Was a problem found? | -- | ||
14 | Replace the Crankshaft Position sensor. Refer to Crankshaft Position (CKP) Sensor Replacement . Is the replacement complete? | -- | -- | |
15 | Check for an open in the Crankshaft Position sensor feed circuit. Was a problem found? | -- | ||
16 | Check for a faulty connection at the VCM. Was a problem found? | -- | ||
17 | Repair the circuit as necessary. Refer to Wiring Repairs in Engine Electrical. Is the action complete? | -- | -- | |
18 | Replace the VCM. Important: If the VCM is faulty, reprogram the VCM. Refer to VCM Replacement/Programming . Is the action complete? | -- | -- | |
19 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||
20 | Using the scan tool, select the Capture Info and the Review Info. Are any DTCs displayed that have not been diagnosed? | -- | Go to the applicable DTC table | System OK |
