What this code means
P1298 may mean the PCM is seeing an electrical load detector circuit signal that is higher than expected or not plausible for the operating condition.
What the vehicle may do
- The vehicle may turn on the check engine light.
- Charging or electrical-load monitoring behavior can seem abnormal.
- The engine may often still run normally.
Possible fault areas
- Possible ELD fault.
- Possible ignition feed issue to the ELD.
- Possible ELD ground issue.
- Possible ELD signal wire issue between the ELD and PCM.
- Possible PCM software or PCM-related issue after circuit checks are proven.
Diagnostic path
Opening context
On this 2010 to 2015 Honda Civic with the 1.8 gas engine, P1298 points to an ELD circuit high-voltage fault. In plain terms, the PCM is seeing an electrical load detector signal that does not make sense for the circuit. The car may have a check engine light, and it can have charging or electrical-load monitoring behavior that seems abnormal, though the engine may often still run normally. The possible fault areas are the ELD itself, its ignition feed, its ground, the signal wire back to the PCM, or in some cases PCM software or the PCM after the circuit checks are proven out. Before getting into pinpoint checks, start with the basic system checks and follow a structured diagnostic approach.
Verify the fault first
Start by duplicating the fault. Turn the ignition switch to ON (II), or use the engine start/stop button to select ON mode. With the HDS, look at ELD, electric load value, in the data list. If it shows 0.2 A or less, the fault is duplicated and you move into circuit testing. If it does not show 0.2 A or less, treat it as intermittent for now. The system is OK at this moment, so check for poor connections or loose terminals at the ELD and the PCM. If captured operating data is available for this code, try to reproduce the fault under those same conditions.
Check the ignition feed to the ELD
Next, check the IG1_ACG feed. Turn the ignition switch to LOCK (0), or select OFF mode, and disconnect the ELD 3P connector. Then turn the ignition back to ON (II), or select ON mode. Measure voltage from ELD 3P connector terminal No. 3, the YEL wire, to body ground. You are looking for battery voltage. If battery voltage is there, the IG1_ACG feed is OK and you continue. If battery voltage is not there, check the No. B2 (10 A) fuse in the under-dash fuse and relay box. If that fuse is OK, repair the open in the IG1_ACG wire between the No. B2 (10 A) fuse and the ELD.
Check the ELD signal wire
Now check the ELD signal wire for an open. Turn the ignition switch to LOCK (0), or select OFF mode. Jump the SCS line with the HDS, then disconnect PCM connector A, the 51P connector. With the ELD 3P connector still disconnected, check continuity between PCM connector A terminal No. 34, the ORN wire, and ELD 3P connector terminal No. 1, also the ORN wire. If you have continuity, the ELD signal wire is OK and you keep going. If you do not have continuity, repair the open in the ELD wire between PCM A34 and the ELD.
Check the ELD ground
Next, check the ground side. With the ignition still in LOCK (0) or OFF mode, the ELD 3P connector disconnected, and PCM connector A disconnected, check continuity between ELD 3P connector terminal No. 2, the BLK wire, and body ground. If continuity is present, the ground wire is OK and you move to the ELD substitution check. If continuity is not present, repair the open in the ground wire between the ELD and G301.
Substitute the ELD and separate the final decision
After the feed, signal, and ground checks pass, substitute a known-good ELD. Turn the ignition switch to ON (II), or select ON mode. Reset the PCM with the HDS, perform the PCM idle learn procedure, and then check for Pending or Confirmed DTCs with the HDS. If P1298 is still indicated, update the PCM if it does not have the latest software, or substitute a known-good PCM. If P1298 goes away after the PCM update, troubleshooting is complete. If it goes away with the known-good PCM substituted, replace the original PCM. If P1298 is not indicated after installing the known-good ELD, replace the original ELD.
Closing takeaway
The key with P1298 is not to condemn the ELD until the ignition feed, signal circuit, and ground path have been proven. Verify the code, work the circuit in order, then confirm the repair and make sure P1298 stays gone. For more diagnostic training, visit stepdiagnostics.com.
Final check
P1298 is best approached by verifying the scan data first, then proving the ELD feed, signal, and ground circuits before making the final component decision.
For more guided automotive diagnostics, visit STEP Diagnostics.
