Schematic Reference: Engine Controls Schematics
Circuit Description
The ignition signal and ignition fail-safe signal provide crucial information in the control of the ignition system timing, injector timing, and fail-safe activation. Based on an initial timing angle calculated from the crankshaft and the camshaft signals, the PCM outputs an ignition signal to the Ignition Control Module (Igniter) as a reference point from which it determines ignition dwell period. A circuit within the Ignition Control Module (Igniter) controls the ignition dwell period by controlling the power transistor switch "ON." When the PCM determines the proper time to provide spark, it turns the ignition signal "OFF," which turns the Ignition Control Module (Igniter) power transistor "OFF," producing a spark. After the spark has occurs, the Ignition Control Module (Igniter) sends an ignition fail-safe signal back to the PCM, confirming that an ignition event has taken place. If the ignition fail-safe signal is not received by the PCM, a fail-safe mode is activated and injection operation is ceased, to protect the catalytic converter.
Conditions for Setting the DTC
No ignition fail-safe signal to the PCM for 4 consecutive ignition cycles, during engine running.
Action Taken When the DTC Sets
| • | The PCM will illuminate the MIL . |
| • | The PCM will store the conditions which were present when the DTC set as Freeze Frame Data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL "OFF" on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present. |
| • | A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault. |
| • | A DTC can be cleared by using the scan tool "Clear Information" function or by disconnecting the PCM battery feed. |
Diagnostic Aids
An intermittent malfunction may be cause by a poor connection, rubbed through wire insulation, or a broken wire inside the insulation. Inspect harness connectors for backed out terminals, improper matting, broken locks, terminal-to wire connection before component replacement.
Inspect for an EFI relay staying ON after the ignition is turned OFF. If the EFI relay is ON with the engine not running, a DTC P1300 will set on the next ignition cycle.
The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.
Test Description
The numbers below refer to the step numbers in the Diagnostic Table.
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The OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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This step checks whether DTC P1300 is the result of a hard failure or an intermittent condition.
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Voltage may vary due to the condition of the start and battery (how well the engine turns over). The battery should be fully charge and no load should be on the engine.
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If the Engine Speed circuit is shorted to ground the engine will not start. This checks whether the Engine Speed Output circuit is shorted to ground.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the "Powertrain On Board Diagnostic (OBD) System Check performed? | -- | |||
Does DTC P1300 set? | -- | Go to Diagnostic Aids | ||
3 |
Does the DMM read within specified value? | 4-6 V | ||
Using a DMM, measure voltage from Ignition Control Module (Igniter) harness connector cavity 2 (harness side) to ground while cranking engine. Does the DMM read within specified value? | 1.5 V | |||
5 | Using a DMM, measure voltage from Ignition Control Module (Igniter) harness connector cavity 5 (harness side). Does DMM read within the specified range? | 10-12 V | ||
6 | Backprobe using a DMM, measure voltage from distributor connector cavity 4 (harness side). Does the DMM read within specified value? | 12 V | ||
7 |
Does the DMM read within specified value? | 12 V | ||
8 | Using a DMM, measure voltage from Ignition Control Module (Igniter) harness connector cavity 3 (harness side). Does DMM read within specified value? | 12 V | ||
Does the engine start? | -- | |||
10 | Repair short in the BLK wire between Ignition Control Module (Igniter) and instrument cluster. Is the action complete? | -- | -- | |
11 |
Was a repair necessary? | -- | ||
12 |
Was a repair necessary? | -- | ||
13 |
Was a repair necessary? | -- | -- | |
14 | Using a DMM, measure voltage from junction block 1 connector C8 cavity 4. Does DMM read within specified value? | 12 V | ||
15 | Using a DMM, measure voltage from ignition switch connector cavity 2. Does DMM read within specified value? | 12 V | ||
16 |
Was a repair necessary? | -- | ||
17 |
Was a repair necessary? | -- | ||
18 |
Was a repair necessary? | -- | ||
19 | Repair the open or short in the power feed to ignition switch. Is the action complete? | -- | -- | |
20 | Replace the junction block 1. Is the action complete? | -- | -- | |
21 | Replace the ignition switch. Is the action complete? | -- | -- | |
22 | Replace the ignition wires. Is the action complete? | -- | -- | |
23 | Replace the Ignition Control Module (Igniter). Is the action complete? | -- | -- | |
24 | Replace the ignition coil. Is the action complete? | -- | -- | |
25 | Replace the PCM. Is the action complete? | -- | -- | |
26 | After repairs, use the scan tool clear information function and road test vehicle within "Freeze Frame" conditions that set the DTC. Check for DTC(s). Review scan tool data and if no DTC(s) are stored repair is complete. Are any DTC(s) displayed on scan tool? | -- | Go to the applicable DTC table | System OK |
