A mysterious, intermittent problem with starting the bike

Problem described

For a while now, Donna’s XT has on occasion refused to start when cold. The pattern seems to be:

• Engine is cold
• Transmission is in neutral
• Kickstand is down
• Clutch is not engaged
• The engine starts but immediately cuts out while the engine fault indicator lights up for a fraction of a second
• No error code is displayed after

Engaging the starter, the engine fires and runs for a second or so and then cuts out. This can be repeated over and over on these occasions when the problem does surface which is maybe once in every 25 cold starts.

Engine cutting out without any error code:

Troubleshooting

To try to figure out what’s going on we invoked the XT’s diagnostic system which works quite well but requires the fuel pump to be disconnected which is a bit of a pain. This is how you do it:

• Disconnect the fuel pump (you have to remover the fuel tank)
• With the ignition off
• Press and hold down the Set and Reset buttons
• Switch the ignition on while keep pressing the buttons until entering diagnostic mode
• Let go of the buttons
• Then press and hold the Set and Reset buttons again until the diagnostic sequence starts
• Move back and forth with the buttons
• Activate actuators with the kill switch

Going through all the diagnostic codes:

We first looked at the stored errors (diagnostic code 61) but found only a lean angle error which made sense since the bike has been down in the past. Then going through all the codes, everything checked out except the signal from the side-stand switch. The diagnostic system displays the output from the side-stand switch as either On or Off, which didn’t consistently correspond with the movement of the kickstand.

Checking the lean-angle sensor:

Time to put the thinking caps on

• According to the service manual, the engine will run both if
  • the transmission is in gear and the side-stand is up and
  • if the transmission is in neutral and the side-stand is down.
• So, at this point we were confused…
  • The engine cuts out while running without displaying an error code
  • The diagnostic system tells us the side-stand switch doesn’t operate correctly
  • But, even if the side-stand switch gives a bad reading to the system, the engine shouldn’t cut out because the the transmission is in neutral. It doesn’t make sense

Our current thinking then is that the built in diagnostic system doesn’t show the result from the side-stand switch directly but instead the result from the combined and resulting logic from the side-stand and neutral switches. That is, it is not the side-stand switch that is defective but instead the neutral switch that intermittently, when cold, gives a bad reading.

• Starting the bike with the kickstand down and the transmission in neutral should work. And,
  • if the side-stand switch gives an incorrect reading, this should be irrelevant, but
  • if the neutral switch gives an intermittent bad reading while the kickstand is down, the engine should cut out.

Next steps

Anyway, that’s our current thinking; we will see. When the weather warms up we will have a look at the neutral switch and I’ll add the findings to this post.

Update June 8, 2021

We replaced the neutral switch and that was it – problem solved!

Diagnostic codes

In the meantime, here is a table of the diagnostic codes available with references to the page(s) in the service manual.

Diagnostic code	Fault code	Description	Pages in Manual
d01:	15, 16	Throttle position sensor	7-37, 7-38
d02:		Atmospheric pressure	7-55
d03:	13, 14	Air intake pressure sensor	7-35, 7-36
d05:	22	Intake air temp sensor	7-40
d07	42	Speed sensor	7-47
d08	30, 41	Latch up detected;  Lean angle sensor	7-42 7-46
d09	43	Fuel system voltage	7-48
d11	28	Engine temp sensor	7-41
d20	20, 19	Sidestand switch	7-38, 7-39
d30	33	Ignition coil	7-43
d36	39	Injector
d50	43	Fuel system voltage	7-48
d52		Headlight relay	7-56
d54		Fast idle solenoid	7-56
d60	44, 46, 50, Er-1, Er-2, Er-3, Er-4,	EEPROM fault code number	7-49 – 7-55
d61		Malfunction history code display	7-56
d62		Malfunction history code erasure	7-56
d70		Control number	7-56