How To Fix A Service Start Stop Message On A Chrysler Pacifica

By Scott Shotton

Batteries that get dead overnight are nil new. Parasitic draws accept been around longer than we have had glove box lamps. I remember, before I really knew much about cars, an old gentleman showing me how to disconnect a battery last and put it back in place while looking for a spark! I am positive this has non been a good technique for many decades and many reasons. But I digress.

Today'south case involves a 2017 Chrysler Pacifica (non-hybrid) equipped with a finish-start arrangement.

The customer's complaint is that the bombardment goes dead overnight but can be jump started and remain functional for the balance of the 24-hour interval. Once parked overnight the symptoms repeat themselves over again. Because I am a mobile technician, and the shop called me on this 1, I requested that they charge and exam the battery to have the vehicle prepare when I arrived. The battery was charged when I arrived and I was told that the battery tested good.

Our diagnostic approach to this vehicle is going to exist testing for a parasitic draw. Ane of the tests that we could use is to disconnect the battery and install an ammeter in line. Just as the "spark" examination mentioned earlier, I no longer like this test. Actually, I adopt not to disconnect whatever vehicle's bombardment unless I absolutely have to. Who knows what memories can be lost, radios locked or adaptive strategies erased?

I prefer a scope and a electric current probe. It is like shooting fish in a barrel to grab a bombardment cable and clamp a current probe around it to meet the resting draw.

In this case the vehicle has two batteries: a main battery and an auxiliary battery that is much smaller. This is going to bear on our diagnostic path. Start, we will need to access a wiring diagram. Effigy one was obtained from OnDemand5 and is quite decorated. I did have to trace some wires around to get the lay of the land. For simplicity, Figure 2 is a re-drawn version of the system.

Fig.1: The wiring diagram for the Pacifica in the bay.(below)

Fig. 2: A re-drawn version of the Pacifica diagram for simplicity. (below)

Note that in Figure two above, I made some annotations (in Blue) of where I will be making connections. These annotations will be referred to throughout this commodity.

Using my PicoScope 4823 scope and a Pico TA189 30-amp current probe (Fig. 3 below) I started doing my testing without disconnecting anything.

Fig. 3: Pico 8-channel scope continued and ready to measure (Enlarge and open in new window)

My first connexion was at Point A of figure 2 and really where the current probe is shown in figure 3. This is the principal basis for the vehicle and I got a reading of approximately 800 milliamps. FCA service data says that around 35 milliamps is acceptable on this vehicle. My next footstep was to motion the probe to Point B and I measured approximately 800 mA. My adjacent step was to movement to Bespeak C and I obtained a 400 mA reading.

At this point, since a 400 mA draw was going through the Ability Distribution Center (PDC) I chose to do a voltage drop test across each fuse to run across which excursion was the culprit. This test, past the mode, is much better than pulling fuses. Removing a fuse can reset a module and completely mess upwards our path. During my testing I constitute that around half of the fuses had a voltage driblet which indicates that current is flowing in those circuits. I guess at present information technology is fourth dimension to plug in a scan tool and run into if nosotros have any codes. I have been trying to avoid this job because I did not want to wake up any modules simply by opening the door.

I connected the wiTech2 and retrieved low battery voltage codes from almost every module. This was no surprise given how many times the battery went dead and had been leap started. My train of idea at this signal was: do nosotros have multiple modules staying awake and causing half of our parasitic draw?

To test my theory, I left the wiTech2 connected, powered down the vehicle and observed the topology screen to come across if modules went to sleep. I waited over thirty minutes and Fig. 4 beneath is what I observed. The modules that are red went to slumber. The modules that are blueish or yellowish are nonetheless awake. If we practise a count, 21 modules are nevertheless awake and nine modules went to sleep. The 21 modules that are still awake could business relationship for our parasitic draw couldn't they?

Fig. iv: Chrysler Topology. (Overstate and open in new window)

My point is, with a dual battery organisation, our approach may demand to exist different. If you look closely at the wiring diagram in figure Fig. 2 (below) you will meet, in the rest position, both batteries are wired in parallel.

In this instance I chose to leave my current probe continued and disconnect the power feed at Bespeak D to eliminate almost the unabridged vehicle. I still observed a 400 mA reading. For reference, the starter and generator excursion were also eliminated from the equation. If we look closely at the diagram given what I have disconnected, is in that location anything left besides the ii batteries wired in parallel? Also, should there be a 400 mA depict between the two?

The shop told me that they tested the bombardment, but if there was a second battery wired in could that effect our results? Time to get back to basics and do some addition research.

First, on a multiple battery system, batteries demand to be disconnected to examination them. In this case the store neglected isolate the batteries and never fifty-fifty tested the second battery. The Aux. Battery on this vehicle was bad. Boosted research explained how the organization works. During cranking the power command relay (Fig. 2) opens to allow the starter motor to utilise the primary battery while the Aux. Bombardment supplies power to everything else on the vehicle. In this case, OCV of the Aux. Battery way half dozen.2 volts when isolated. Do modules similar that voltage?

Second, if ii batteries are wired in parallel and one of the batteries has failed, will the good battery try to charge the bad bombardment even in a land of balance? Yes!

What was happening on this vehicle? The bad battery was draining the good battery hence the measured 400 mA draw at Point B of Fig. 2 with disconnection at Signal D . That accounted for half of our describe. The second half of the 800 mA draw was due to modules staying awake as shown in Fig. 4. Why were they staying awake?

Research into system functioning revealed that during cranking the power control relay opens. At this point, the main bombardment powers the starter motor to creepo the engine over. The Aux. Bombardment is isolated and is responsible for powering all of the modules on the vehicle. If the Aux. Battery has too low of a voltage modules become confused and, in this instance, stayed awake causing the 2nd 400 mA draw measured at Point C of Fig. 2.

The full is the 800 mA depict that is draining the battery. The failed Aux. Bombardment was the cause of both draws. Replacement of the battery, the shop opted to replace both, resolved the issue. My bespeak is: exist aware of how multiple batteries conduct when wired together, isolate them for testing purposes and do not be surprised when low battery voltage causes unusual electronic module behavior.