Now that we've had a bit of a cold snap here in Florida, I've noticed that the little orange "wait to start" coil indicator on the dash doesn't stay on when I turn the key on. When I start my truck, it seems to labor a little bit before starting up.

Any ideas on what I need to replace so the truck knows it's cold outside and turns on the intake grid heater?

 

Oh, for what it's worth, the truck isn't setting any codes... It just seems as if it doesn't know it's 40deg outside...

 

Just a thought here.....just because it's 40 outside doesn't necessarily mean it's 40 at the grid heater location, especially if it hasn't been 40 very long. It think the temp at the intake horn , not the outside temp, has to be below 59F for the grid heaters to come on.

If indeed the air temp at the intake horn is below 59 and the grid heaters are not coming on, then maybe it's the sensor?

Alternately, maybe the WTS light bulb is out?

Good luck!

 

If I understand you correctly your "wait to start" light still does the bulb check but doesn't stay on. If so, I would start by checking the iat sensor on your intake. I'm curious does your post heat cycle work ?

 

When you first turn the key on does your voltage drop on the gauge indicating a draw from the grid heater?

It should start with little problem at 40 degrees anyway, trust me -40 is a whole different matter!

 

WTS bulb is not out, it does come on briefly when the key is turned on...

Def. not -40deg here or anything, but in previous years it would always stay on in weather like this, whereas now it isn't. The grid heaters do appear to be working somewhat, as I can see the normal fluctuations in the voltage gauge (and the dimming headlights) when the truck is first started.

I didn't know it was the IAT sensor that the truck used to determine whether or not to turn on the grid heaters. I think I'll replace the IAT sensor and see if that takes care of things.

 

May not be the grid heater for the reason behind the hard start.

 

You may be able to clean the IAT and/or the connector and get the grid heaters to function. Some use an oiled aftermarket intake that has been Known to coat the IAT and distort it's readings. IDK what type of intake you use but it won't hurt to clean the IAT and the connector. Keep us up to date.

 

Well, the hard to start part of the equation was the batteries. They decided to die on me, so I replaced them both.

I haven't had a chance to try and test the IAT sensor yet. I'll try cleaning it first, but I have a friend here with a similar truck I can swap out sensors with to see if that fixes things.

 

Well, swapping out the IAT sensor netted no change at all... The wait to start light still does not stay on on those cold mornings...

From what I can see from the factory service manual, the operation of the wait to start circuit is solely based on the IAT sensor reading, so I'm not sure what to try next. It's not annoying enough that I would replace the ECM to fix the problem.

 

I am in South Florida ... same cold snap ... my problem is 3 days ago my WTS indicator stopped coming on at all. No quick on then off ... no nothing.

 

here is the operation of the grid heater via Dealerconnect.


OPERATION
The wait-to-start indicator gives an indication to the vehicle operator when the air temperature within the diesel engine intake manifold is too cool for efficient and reliable engine starting, and that the intake air heater grids are energized in their pre-heat operating mode. This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the Engine Control Module (ECM) over the Programmable Communications Interface (PCI) data bus.

The wait-to-start indicator Light Emitting Diode (LED) is completely controlled by the instrument cluster logic circuit, and that logic will only allow this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the LED will always be off when the ignition switch is in any position except On or Start. The LED only illuminates when it is provided a path to ground by the instrument cluster transistor. The instrument cluster will turn on the wait-to-start indicator for the following reasons:

Wait-To-Start Lamp-On Message - Each time the cluster receives a wait-to-start lamp-on message from the ECM indicating that the air temperature within the intake manifold is too cool for efficient and reliable engine starting, the wait-to-start indicator will be illuminated. The indicator remains illuminated until the cluster receives a wait-to-start lamp-off message, until the ECM detects that the engine is running or until the ignition switch is turned to the Off position, whichever occurs first.
Actuator Test - Each time the cluster is put through the actuator test, the wait-to-start indicator will be turned on, then off again during the bulb check portion of the test to confirm the functionality of the LED and the cluster control circuitry.
The ECM continually monitors the engine intake air temperature sensor to determine when the intake air heater grids should be energized in their pre-heat operating mode. The ECM then sends the proper wait-to-start lamp-on and lamp-off messages to the instrument cluster. For further diagnosis of the wait-to-start indicator or the instrument cluster circuitry that controls the indicator, (Refer to 8 - ELECTRICAL/INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING).

For proper diagnosis of the engine intake air temperature sensor, the intake air heater grid control circuits, the ECM, the PCI data bus, or the electronic message inputs to the instrument cluster that control the wait-to-start indicator, a diagnostic scan tool is required. Refer to the appropriate diagnostic information.

 

i have been still searching but yet to find an exact temp number as to when it is supposed to come on. still lookin though

 

I dont think the IAT is the only thing it looks at for the grid heater. It uses the coolant temp and MAP temp too. MAP temp sensor is probably the culprit. You can tell with a scan-tool. The MAP temp shows up as IAT on a scanner.

 

I did a dash test on mine and the light comes on ... I think it is dealer time ... let them figure it out.