Engine wiring diagrams schematic for pin 5 signal ground

K24C_R_V

MEMBER
2005 HONDA CRV
2.4L
4 CYL
2WD
AUTOMATIC
140,000 MILES

Car was brought to dealership with no crank no start, they were able to get car to start only with obd2 plugged in. Checked both grounds on obd2 port chassis ground is good but signal ground is not. Signal ground to battery ground starts the vehicle. When vehicle is tried to start without scanner just cranks and does not fire while doing this if scanner is plugged in immobilizer will disable starting until ignition is turned off then back on. Only engine code is P0499 which has been on for awhile with no issue.

Found schematic for pin 5 signal ground but unsure where grounding issue would be within circuit.

1 Reply

KEN L

MASTER CERTIFIED MECHANIC
42,967 POSTS

It sound like the scanner is supplying ground or power to the PCM. This can be caused by a bad ground or lack of power. There are two PGM-FI relays. I would check first; here is the engine and ALDL connector wiring so you can see how the system works and a guide on how to test the relays:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Here are the engine wiring diagrams and fuse and relay locations also check all fuses and the power to the ALDL and PCM:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Check out the diagrams (below). Please let us know what happens.

Cheers, Ken

Images (Click to make bigger)