PGM-FI System Description - On-Board Snapshot
Overview
For an easy analysis of problems, the PCM has three types of on-board snapshots: the on-board snapshot when DTC is stored, the on-board snapshot when engine stalls, and the on-board snapshot when engine does not start.
- The on-board snapshot for DTC is recorded only for the first DTC.
- The on-board snapshot for engine stall and engine does not start are overwritten and cleared by a new one.
- The data of each on-board snapshot can be checked and cleared with the HDS. Be sure to clear the on-board snapshot after checking it because the data storage capacity is limited.
Control - On-board snapshot when the engine stalls
The preconditions for recording an on-board snapshot when the engine stalls are shown below. When an engine stall occurs under these preconditions, the parameters related to the engine stall are stored in the PCM - for a time span extending for 9 seconds before the engine stall and 1 second after the engine stall - covering a total of 10 seconds.
The precondition is:
- 5 seconds have elapsed after engine start (engine speed 500 rpm or higher) (In case of an engine stall within 5 seconds after the engine started, this is memorized on the side of the on-board snapshot when engine does not start (engine starts but stalls immediately))
- Engine speed at the time of an engine stall is below 3,000 rpm
- After 1 drive cycle, after PCM reset, or 12 volt battery terminal disconnection.
- SCS is not shorted
*: In case of an engine stall for a vehicle with a manual transmission at a vehicle speed of 3.1 mph (5 km/h) or lower, the on-board snapshot is not memorized.
Control - On-board snapshot when the engine does not start
The three types of 'engine is hard to start', engine will not start, and engine start but stalls immediately are set for an on-board snapshot at the time of engine starting problems.
The preconditions for recording an on-board snapshot when the engine does not start are as shown below, and when engine starting problems occur under these preconditions, the parameters related to the engine starting problems are stored in the PCM.
The precondition is:
- After 1 drive cycle, after PCM reset, or 12 volt battery terminal disconnection.
- On-board snapshot of Engine stalls is not stored.
- SCS is not shorted
The on-board snapshot when engine does not start has the timer for the evaluation of starting problems as a factor is variable, and it depends on the engine coolant temperature when the engine starts, the relation between the engine coolant temperature and the engine start time; as it is shown below.
| Initial engine coolant temperature (°F (°C)) | -40(-40) | -22(-30) | -13(-25) | -4(-20) | 5(-15) | 14(-10) | 194(90) |
| Engine start time (sec.) | 6.0 | 6.0 | 3.0 | 2.25 | 1.5 | 1.5 | 1.5 |
On-board Snapshot Recording Zone
The on-board snapshot when engine does not start functions during the first cranking after the vehicle ON mode, though it is nonfunctional when cranking the second and later in the same vehicle ON mode. If the on-board snapshot goes back to a state of possible recording again, it needs to go through once the vehicle OFF (LOCK) mode.
On-board snapshot of engine is hard to start and engine will not start:
An on-board snapshot is taken when an engine does not start or when an engine is hard to start. The snapshot is taken when cranking (engine speed 500 rpm or lower) takes longer than the specified time (timer for the evaluation of starting problems: variable according to the conditions at the time of start). If it is determined that a starting problem exists, the parameters related to the starting problem (for 9 seconds before the evaluation of the starting problem and 1 second after the evaluation of starting problem) are stored in the PCM, covering a total of 10 seconds.
On-board snapshot of engine starts but stalls immediately:
An on-board snapshot is taken when an engine stall occurs within 5 seconds after the engine is started, although the engine started (engine speed 500 rpm or higher) with cranking (engine speed 500 rpm or lower) within the specified time (timer for evaluation of starting problems: variable according to the conditions at the time of start). The parameters related to the stall after a complete combustion process for the 9 seconds before the engine stall and 1 second after the engine stall are stored in the PCM, covering a total of 10 seconds.