87121-ZV4-A01 Honda MARK, RR. (15) (Honda Code 6250294).

Test Step 1. Use Caterpillar Electronic Technician (ET) to Check the Output of the Transformers
Remove the electrical power from the engine.
Connect Cat ET to the service tool connector.
Restore the electrical power to the engine. Set the engine control to STOP.
Set up two status screens for Cat ET. Use eight of the following labels for parameters on each Status screen:
Table 1
Parameters for the Status Screens on Cat ET
Screen 1 Screen 2
"Cylinder #1 Transformer Secondary Output Voltage Percentage" "Cylinder #2 Transformer Secondary Output Voltage Percentage"
"Cylinder #3 Transformer Secondary Output Voltage Percentage" "Cylinder #4 Transformer Secondary Output Voltage Percentage"
"Cylinder #5 Transformer Secondary Output Voltage Percentage" "Cylinder #6 Transformer Secondary Output Voltage Percentage"
"Cylinder #7 Transformer Secondary Output Voltage Percentage" "Cylinder #8 Transformer Secondary Output Voltage Percentage"
"Cylinder #9 Transformer Secondary Output Voltage Percentage" "Cylinder #10 Transformer Secondary Output Voltage Percentage"
"Cylinder #11 Transformer Secondary Output Voltage Percentage" "Cylinder #12 Transformer Secondary Output Voltage Percentage"
Start the engine. Allow the engine to warm up to normal operating temperature. Apply the normal load at rated speed.
Observe the value of the output for the secondary circuit of each transformer. Expected Result:The displayed value of the output for the secondary circuit of each transformer is between 1 and 90 percent.Results:
OK - The displayed value of the output for the secondary circuit of each transformer is between 1 and 90 percent.Repair: The ignition system components are operating properly. Investigate other possible root causes of the problem. Troubleshoot the symptom. Refer to Troubleshooting, "Symptom Troubleshooting".STOP
Not OK - At least one of the outputs displayed a value of 0 percent or a value that is greater than 90 percent. The ignition system components require maintenance. Proceed to Test Step 2.Test Step 2. Inspect the Condition of the Transformer
Ignition systems can cause electrical shocks. Avoid contacting the ignition system components and wiring.Do not attempt to remove the valve covers when the engine is operating. The transformers are grounded to the valve covers. Personal injury or death may result and the ignition system will be damaged if the valve covers are removed during engine operation. The engine will not operate without the valve covers.
Remove the electrical power from the engine.
Illustration 1 g02622899
Location of the components of the ignition transformer
(1) 2-pin connector
(2) Transformer
Remove the valve cover from the suspect cylinder.
Pulling on the wiring harness may break the wires. Do not pull on the wiring harness.
Disconnect 2-pin connector (1). Remove transformer (2) from the engine.
Illustration 2 g01425994
Ignition transformer and extension
(3) Transformer
(4) Screws for the ground spring
(5) Ground spring
(6) Spacer
(7) Connector for the spark plug
(8) Extension
(9) O-ring seal
Inspect the body of transformer (3). Check that the screws (4) for ground spring (5) are tight and secure. Verify that there is no visible corrosion or damage to the transformer.
Check that the connector (7) that is for the spark plug is free of corrosion and/or for damage.
Inspect O-ring seal (9) inside extension (8) for damage.
Check for a secure connection between the transformer and the spark plug.
Check extension (8) near spacer (6) for signs of pin holes that can be caused by arcing.
The extension can be scratched and damaged with a wire brush. Do not use a wire brush on the extension.
Clean any deposits from the inside of the extension. Use a 6V-7093 Brush with isopropyl alcohol. Expected Result:The transformer is in good condition.Results:
OK - The transformer is in good condition. Proceed to Test Step 3.
Not OK - The transformer is in poor condition.Repair: The inspection found a problem with the transformer. Repair the transformer, when possible. Replace the transformer, if necessary. Be sure to use the correct transformer for the CG137 Engine.Reset the control system. Restart the engine. Clear the logged codes.STOPTest Step 3. Test the Primary Circuit and the Secondary Circuit of the Transformer
Illustration 3 g01425156
Schematic of the circuit for the ignition transformer
Measure the primary circuit by checking the voltage of the blocking diode.